The graphical representation of a function that represents direct proportionality is actually the ability to express an algebraic expression through a graph.

As it is a direct proportionality, the graph will be of a straight line.

A function that represents direct proportionality is a linear function of the family y=ax+b y=ax+b .

The graphical representation of this function is a straight line that is ascending, descending, or parallel to the X X axis but never parallel to the Y Y axis.

Note: we observe the line from left to right.

We can now recognize in the equation of the line what the graphical representation of each function looks like:

(only when the equation is explicit Y Y is isolated on one side and its coefficient is 1 1 )

A - Graphs of Direct Proportionality Functions

Suggested Topics to Practice in Advance

  1. Function
  2. Linear Function
  3. The Linear Function y=mx+b
  4. Slope in the Function y=mx
  5. Positive and Negativity of a Linear Function
  6. Finding a Linear Equation

Practice Graphical Representation

Examples with solutions for Graphical Representation

Exercise #1

Choose the correct answer

xy

Step-by-Step Solution

The blue line is a straight line, therefore it remains constant.

Let's note that the red line is rising because it starts in the negative part (negative values) and rises to the positive part (positive values).

Therefore, the correct answer is D.

Answer

Answers B and C are correct

Exercise #2

Which graph represents an increasing function that intersects the origin of the axes?

xy

Step-by-Step Solution

To solve this problem, we need to identify which graph fulfills two criteria: intersecting the origin and having a positive slope (i.e., being an increasing function).

Let's examine the provided graphs:

  • Criterion 1: Intersects the Origin
    A graph that intersects the origin will pass through the point (0,0)(0,0). This means that when x=0x = 0, yy should also be 00.

  • Criterion 2: Increasing Function
    An increasing function is indicated by a line that has a positive slope. This means that as xx increases, yy should also increase.

Analysis of Graphs:

  • The Green Graph: This graph passes through the point (0,0) but moves from the top left to the bottom right, which represents a negative slope.

  • The Blue Graph: This graph also does not pass through the origin; it intersects the y-axis above the origin point.

  • The Yellow Graph: This graph intersects below the origin and slants negatively, indicating a negative slope.

  • The Red Graph: This graph passes through the point (0,0) and moves from the bottom left to the top right, which confirms a positive slope. Therefore, it is an increasing function that intersects the origin.

Based on the analysis above, the graph that represents an increasing function that intersects the origin is confidently identified as the red graph.

Therefore, the correct choice is the red graph \text{the red graph} .

Answer

The red graph.

Exercise #3

At what point does the graph intersect the x axis?



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Video Solution

Step-by-Step Solution

Note that the line intersects only the Y-axis. In other words, it does not go through the X-axis at all.

Therefore, the answer is (d).

Answer

It does not intersect the x axis.

Exercise #4

Does line I pass through the origin point of the axes?

111222333444555666777–5–5–5–4–4–4–3–3–3–2–2–2–1–1–1111222333000xyIII

Video Solution

Step-by-Step Solution

Let's first remember that the origin of the coordinate system is (0,0) (0,0) .

We'll highlight the point on the graph, noting that it doesn't lie on any of the plotted lines.

Therefore, the answer is C; If we plot the point (3,1) (3,1) , then we'll see that it lies on line I (the blue one).

Answer

No, it passes through (3,1) (3,1) .

Exercise #5

At which point does the graph of the first function (I) intersect the graph of the second function (II)?

111222333444555666777–5–5–5–4–4–4–3–3–3–2–2–2–1–1–1111222333000xyIII

Video Solution

Step-by-Step Solution

Let's pay attention to the point where the lines intersect. We'll mark it.

We'll find that:

X=4,Y=2 X=4,Y=2

Therefore, the point is:

(4,2) (4,2)

Answer

(4,2) (4,2)

Exercise #6

What representations describe a linear function?

Video Solution

Step-by-Step Solution

To solve this problem, we need to determine which representations describe a linear function by analyzing each given choice:

  • Choice 1: y=12x y = 1 - 2x
    - This is in the form y=mx+b y = mx + b , where m=2 m = -2 and b=1 b = 1 , making it a linear function.
  • Choice 2: y=2x2+x y = -2x^2 + x
    - The term x2 x^2 indicates a quadratic polynomial, which is not linear due to the power of 2 on x x .
  • Choice 3: y=x y = x
    - In the form y=mx+b y = mx + b , it is y=1x+0 y = 1x + 0 , with m=1 m = 1 and b=0 b = 0 , thus a linear function.
  • Choice 4: Asserts that both Choice 1 and Choice 3 are correct, which aligns with our analysis.

Based on this examination, choices forming linear functions are ones where the equation stays in the standard linear form y=mx+b y = mx + b with no additional exponents or variable products. Thus, the correct answer is:

Answers A + C are correct

Answer

Answers A + C are correct

Exercise #7

Which statement is true according to the graph below?

111222333444555666777111222333444555666777888000

Video Solution

Step-by-Step Solution

If we plot all the points, we'll notice that point (3,5) (3,5) is the correct one, because:

x=3,y=5 x=3,y=5

And they intersect exactly on the line where the graph passes.

Answer

The graph passes through (3,5) (3,5) .

Exercise #8

Determine which of the following expressions describes a linear function?

Video Solution

Step-by-Step Solution

Note that in answer A there is an exponent, therefore the answer is incorrect.

Note that in answer C, if we multiply X by X we get X to a power, therefore the answer is incorrect.

Note that in answer D there is an exponent, therefore the answer is incorrect.

In answer B the following formula can be observed.

y=mx+b y=mx+b

Answer

y=4x+1 y=4x+1

Exercise #9

Which of the following represent linear functions and parallel lines?

Video Solution

Step-by-Step Solution

To solve this problem, we'll analyze each pair of given equations to see if they are linear and parallel.

Let's examine each pair:

  • Choice 1:
    y=12x+10 y = \frac{1}{2}x + 10
    y=12(x+2) y = \frac{1}{2}(x + 2) simplifies to y=12x+1 y = \frac{1}{2}x + 1
    Both equations are linear with the same slope of 12 \frac{1}{2} , indicating they are parallel.
  • Choice 2:
    y=3(x+4) y = 3(x + 4) simplifies to y=3x+12 y = 3x + 12
    y=3x2+12 y = 3x^2 + 12 is not in the form y=mx+b y = mx + b as it includes an x2 x^2 term. Thus, it is non-linear.
  • Choice 3:
    y=5+12x y = 5 + 12x is already in the form y=mx+b y = mx + b with m=12 m = 12
    y=5+12+x y = 5 + 12 + x simplifies to y=x+17 y = x + 17 , which has a slope of 1.
    Slopes are different, so not parallel.
  • Choice 4:
    y=3x+2 y = 3x + 2 , slope m=3 m = 3
    y=2x+3 y = 2x + 3 , slope m=2 m = 2
    Different slopes, thus not parallel.

Therefore, based on our analysis, the correct choice is Choice 1:

y=12x+10 y = \frac{1}{2}x + 10 and y=12(x+2) y = \frac{1}{2}(x + 2)

Answer

y=12x+10 y=\frac{1}{2}x+10

y=12(x+2) y=\frac{1}{2}(x+2)

Exercise #10

Given the line parallel to the line y=4 y=4

and passes through the point (1,2) (1,2) .

Which of the algebraic representations is the corresponding one for the given line?

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the key characteristics of the line parallel to y=4 y = 4 .
  • Step 2: Use the point (1,2) (1,2) to determine the new horizontal line equation.
  • Step 3: Write the equation based on the consistent y-value of the line.

Now, let's work through each step:

Step 1: The given line y=4 y = 4 is a horizontal line. All horizontal lines have equations in the form y=c y = c , where c c is a constant value describing the uniform y-position of the line.

Step 2: A line parallel to y=4 y = 4 that also passes through the point (1,2) (1,2) would maintain a constant y-value. Since it must pass through (1,2) (1,2) , its y-intercept is y=2 y = 2 .

Step 3: Therefore, the equation of the line parallel to y=4 y = 4 through (1,2) (1,2) is simply y=2 y = 2 . This ensures it parallels the horizontal direction.

Thus, the algebraic representation of the line parallel to y=4 y=4 and passing through the point (1,2) (1,2) is y=2 y = 2 .

Answer

y=2 y=2

Exercise #11

A straight line with a slope of 2y passes through the point (3,7) (3,7) .

Which equation corresponds to the line?

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Write the equation using point-slope form
  • Step 2: Substitute the given point and slope into the equation
  • Step 3: Simplify to find the slope-intercept form of the line equation

Now, let's work through each step:

Step 1: Use the point-slope form of a line equation, given by yy1=m(xx1)y - y_1 = m(x - x_1), where (x1,y1)(x_1, y_1) is a point on the line.

Step 2: Given that the slope is represented as 2y2y and the line passes through point (3,7)(3, 7), we should interpret it as the slope being equivalent to 2 (as 2y2y in relation suggests y=2x+by=2x+b structure supposedly intended this way). This gives us a slope m=2m = 2.

Using point (3,7)(3, 7), we substitute into the formula:

y7=2(x3) y - 7 = 2(x - 3)

Step 3: Simplify the equation:

y7=2x6 y - 7 = 2x - 6

y=2x6+7 y = 2x - 6 + 7

y=2x+1 y = 2x + 1

Therefore, the equation of the line is y=2x+1 y = 2x + 1 .

Answer

y=2x+1 y=2x+1

Exercise #12

A straight line with the slope 9 passes through the point (5,8) (-5,-8) .

Which of the following equations corresponds to the line?

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Identify the given information
  • Step 2: Apply the point-slope formula
  • Step 3: Convert to slope-intercept form and verify against the given choices

Now, let's work through each step:
Step 1: The problem states the line passes through point (5,8)(-5, -8) and has a slope of 99.
Step 2: Using the point-slope form equation, yy1=m(xx1)y-y_1 = m(x-x_1), plug in (x1,y1)=(5,8)(x_1, y_1) = (-5, -8) and m=9m = 9. So the equation becomes:

y(8)=9(x(5)) y - (-8) = 9(x - (-5))

Which simplifies to:

y+8=9(x+5) y + 8 = 9(x + 5)

Simplifying further gives:

y+8=9x+45 y + 8 = 9x + 45

Then, bring the 88 to the right side to solve for yy in terms of xx:

y=9x+458 y = 9x + 45 - 8 y=9x+37 y = 9x + 37

Therefore, the equation of the line in slope-intercept form is y=9x+37y = 9x + 37, which corresponds to choice 11.

Therefore, the solution to the problem is y=9x+37y = 9x + 37.

Answer

y=9x+37 y=9x+37

Exercise #13

Given the line parallel to the line y=2x+5 y=2x+5

and passes through the point (4,9) (4,9) .

Which of the algebraic representations is the corresponding one for the given line?

Video Solution

Step-by-Step Solution

To solve this problem, let's proceed through these steps:

  • Step 1: Identify the slope of the original line. From y=2x+5 y = 2x + 5 , the slope m m is 2 2 .
  • Step 2: Since parallel lines have the same slope, the line we're looking for will also have a slope of 2 2 .
  • Step 3: Use the point-slope formula with the given point (4,9) (4, 9) :

We begin with the point-slope formula:

yy1=m(xx1) y - y_1 = m(x - x_1)

Substitute m=2 m = 2 , x1=4 x_1 = 4 , and y1=9 y_1 = 9 into the equation:

y9=2(x4) y - 9 = 2(x - 4)

Simplify the equation:

y9=2x8 y - 9 = 2x - 8

Solving for y y , we obtain:

y=2x8+9 y = 2x - 8 + 9

y=2x+1 y = 2x + 1

Therefore, the algebraic representation of the line parallel to y=2x+5 y = 2x + 5 that passes through (4,9) (4, 9) is:

y=2x+1 y = 2x + 1

Answer

y=2x+1 y=2x+1

Exercise #14

Given the line parallel to the line y=3x+4 y=3x+4

and passes through the point (12,1) (\frac{1}{2},1) .

Which of the algebraic representations is the corresponding one for the given line?

Video Solution

Step-by-Step Solution

To solve this problem, we begin by noting that since the line is parallel to y=3x+4 y = 3x + 4 , it must have the same slope, m=3 m = 3 .

We use the point-slope form of the equation of a line, which is:

yy1=m(xx1) y - y_1 = m(x - x_1)

Here, the slope m=3 m = 3 and the line passes through the point (12,1) \left(\frac{1}{2}, 1\right) . Therefore, we substitute these values into the point-slope formula:

y1=3(x12) y - 1 = 3\left(x - \frac{1}{2}\right)

Next, we simplify this equation:

  • Distribute the slope 3 3 on the right side:
  • y1=3x32 y - 1 = 3x - \frac{3}{2}
  • Add 1 to both sides to solve for y y :
  • y=3x32+1 y = 3x - \frac{3}{2} + 1
  • Simplify 32+1-\frac{3}{2} + 1:
  • y=3x12 y = 3x - \frac{1}{2}

Thus, the equation of the line parallel to y=3x+4 y = 3x + 4 and passing through the point (12,1) \left(\frac{1}{2}, 1\right) is:

y=3x12 y = 3x - \frac{1}{2}

The corresponding choice is:

y=3x12 y=3x-\frac{1}{2}

Answer

y=3x12 y=3x-\frac{1}{2}

Exercise #15

A line has a slope of 12 \frac{1}{2} and passes through the point (5,1712) (5,17\frac{1}{2}) .

Which expression corresponds to the line?

Video Solution

Step-by-Step Solution

To determine the line's equation, we'll follow these steps:

  • Use the point-slope form of a line, given by yy1=m(xx1) y - y_1 = m(x - x_1) .
  • Substitute m=12 m = \frac{1}{2} , x1=5 x_1 = 5 , and y1=1712 y_1 = 17\frac{1}{2} into the equation.
  • Solve for y y to put the equation in slope-intercept form.

Now, let's work through the steps:

Given the point (5,1712) (5, 17\frac{1}{2}) and slope m=12 m = \frac{1}{2} , our start point is the point-slope form:
y1712=12(x5) y - 17\frac{1}{2} = \frac{1}{2}(x - 5) .

Convert the mixed number to an improper fraction: 1712=352 17\frac{1}{2} = \frac{35}{2} .

Thus, the equation becomes y352=12(x5) y - \frac{35}{2} = \frac{1}{2}(x - 5) .

Distribute the slope on the right-hand side:
y352=12x52 y - \frac{35}{2} = \frac{1}{2}x - \frac{5}{2} .

To solve for y y , add 352 \frac{35}{2} to both sides:
y=12x52+352 y = \frac{1}{2}x - \frac{5}{2} + \frac{35}{2} .

Combine the fractions on the right-hand side:
y=12x+302 y = \frac{1}{2}x + \frac{30}{2} , which simplifies to y=12x+15 y = \frac{1}{2}x + 15 .

Therefore, the equation of the line in slope-intercept form is y=12x+15 y = \frac{1}{2}x + 15 .

Comparing this with the multiple-choice options, the correct answer is:

y=12x+15 y = \frac{1}{2}x + 15

Answer

y=12x+15 y=\frac{1}{2}x+15