Inputing Values into a Function

In mathematics, we often assign numerical values to variables in equations or mathematical expressions. A function can be thought of as a machine: you input a value (called the input), the function processes it according to a specific rule, and produces a result (called the output). The input is usually represented by \(x)\, and the output by f(x)f(x) or yy.

Understanding Variables and Substitution

A variable is a placeholder for an unknown number, often called the "unknown". When we replace a variable with a specific value, we refer to this process as substitution.

  • If an equation contains only one variable, we can solve for its value by isolating it.
  • If an equation contains multiple variables, there can be multiple solutions. Each value substituted affects the remaining variables in the equation.

When we talk about inputting values into a function, we are essentially substituting the variables in a mathematical expression or equation with specific numerical values to evaluate the result.
Often "solving an equation" is actually finding the values of the variables inside it.

For example

Suppose we have three variables, two of which have known values:

X=3 X=3

Y=2 Y=2

Z=? Z=\text{?}

We are also given the equation:

X2+Y=Z X^2+Y=Z

Remember! when facing this kind of questions, you want to try and find the values of the variables.
To solve the problem, we will first substitute the known values into the equation:

32+2=Z 3^2+2=Z

Simplify and solve:

9+2=Z9+2=Z

Z=11Z=11

By substituting the known values and performing the necessary operations, we were able to isolate and calculate the value of ZZ

Answer: Z=11 Z=11

X Y Z By assigning the numerical value, the general form becomes a particular case

Suggested Topics to Practice in Advance

  1. Ways to Represent a Function
  2. Representing a Function Verbally and with Tables
  3. Graphical Representation of a Function
  4. Algebraic Representation of a Function
  5. Notation of a Function
  6. Rate of Change of a Function
  7. Variation of a Function
  8. Rate of change represented with steps in the graph of the function
  9. Rate of change of a function represented graphically
  10. Constant Rate of Change
  11. Variable Rate of Change
  12. Rate of Change of a Function Represented by a Table of Values
  13. Functions for Seventh Grade
  14. Increasing and Decreasing Intervals (Functions)
  15. Increasing functions
  16. Decreasing function
  17. Constant Function
  18. Decreasing Interval of a function
  19. Increasing Intervals of a function

Practice Inputing Values into a Function

Examples with solutions for Inputing Values into a Function

Exercise #1

6x+5=1 \frac{6}{x+5}=1

What is the field of application of the equation?

Video Solution

Step-by-Step Solution

To solve this problem, we will determine the domain, or field of application, of the equation 6x+5=1 \frac{6}{x+5} = 1 .

Step-by-step solution:

  • Step 1: Identify the denominator. In the given equation, the denominator is x+5 x+5 .
  • Step 2: Determine when the denominator is zero. Solve for x x by setting x+5=0 x+5 = 0 .
  • Step 3: Solve the equation: x+5=0 x+5 = 0 gives x=5 x = -5 .
  • Step 4: Exclude this value from the domain. The domain is all real numbers except x=5 x = -5 .

Therefore, the field of application of the equation is all real numbers except where x=5 x = -5 .

Thus, the domain is x5 x \neq -5 .

Answer

x5 x\operatorname{\ne}-5

Exercise #2

x+y:32x+6=4 \frac{x+y:3}{2x+6}=4

What is the field of application of the equation?

Video Solution

Step-by-Step Solution

To solve this problem, we'll follow these steps to find the domain:

  • Step 1: Recognize that the expression x+y:32x+6=4\frac{x+y:3}{2x+6}=4 involves a fraction. The denominator 2x+62x + 6 must not be zero, as division by zero is undefined.
  • Step 2: Set the denominator equal to zero and solve for xx to find the values that must be excluded: 2x+6=02x + 6 = 0.
  • Step 3: Solve 2x+6=02x + 6 = 0:
    • 2x+6=02x + 6 = 0
    • 2x=62x = -6
    • x=3x = -3
  • Step 4: Conclude that the domain of the function excludes x=3x = -3, meaning x3x \neq -3.

Thus, the domain of the given expression is all real numbers except x=3x = -3. This translates to:

x3 x\operatorname{\ne}-3

Answer

x3 x\operatorname{\ne}-3

Exercise #3

3x:4y+6=6 \frac{3x:4}{y+6}=6

What is the field of application of the equation?

Video Solution

Step-by-Step Solution

To determine the field of application of the equation 3x:4y+6=6\frac{3x:4}{y+6}=6, we must identify values of yy for which the equation is defined.

  • The denominator of the given expression is y+6y + 6. In order for the expression to be defined, the denominator cannot be zero.
  • This leads us to solve the equation y+6=0y + 6 = 0.
  • Solving y+6=0y + 6 = 0 gives us y=6y = -6.
  • This means y=6y = -6 would make the denominator zero, thus the expression would be undefined for this value.

Therefore, the field of application, or the domain of the equation, is all real numbers except y=6y = -6.

We must conclude that y6 y \neq -6 .

Comparing with the provided choices, the correct answer is choice 3: y6 y \neq -6 .

Answer

y6 y\operatorname{\ne}-6

Exercise #4

Look at the following function:

5x \frac{5}{x}

Does the function have a domain? If so, what is it?

Video Solution

Step-by-Step Solution

Since the unknown variable is in the denominator, we should remember that the denominator cannot be equal to 0.

In other words, x0 x\ne0

The domain of the function is all those values that, when substituted into the function, will make the function legal and defined.

The domain in this case will be all real numbers that are not equal to 0.

Answer

Yes, x0 x\ne0

Exercise #5

Does the given function have a domain? If so, what is it?

9x4 \frac{9x}{4}

Video Solution

Step-by-Step Solution

Since the function's denominator equals 4, the domain of the function is all real numbers. This means that any one of the x values could be compatible.

Answer

No, the entire domain

Exercise #6

Look at the following function:

5+4x2+x2 \frac{5+4x}{2+x^2}


Does the function have a domain? If so, what is it?

Video Solution

Step-by-Step Solution

Since the denominator is positive for all x x , the domain of the function is the entire domain.

That is, all values of x x . Therefore, there is no domain limits.

Answer

No, the entire domain

Exercise #7

Given the following function:

65(2x2)2 \frac{65}{(2x-2)^2}

Does the function have a domain? If so, what is it?

Video Solution

Step-by-Step Solution

The denominator of the function cannot be equal to 0.

Therefore, we will set the denominator equal to 0 and solve for the domain:

(2x2)20 (2x-2)^2\ne0

2x2 2x\ne2

x1 x\ne1

In other words, the domain of the function is all numbers except 1.

Answer

Yes, x1 x\ne1

Exercise #8

xyz2(3+y)+4=8 \frac{xyz}{2(3+y)+4}=8

What is the field of application of the equation?

Video Solution

Step-by-Step Solution

To find the domain of the given equation xyz2(3+y)+4=8 \frac{xyz}{2(3+y)+4}=8 , we need to ensure the denominator is not zero. This means solving 2(3+y)+4=0 2(3+y) + 4 = 0 .

Let's solve this step-by-step:

  • Step 1: Simplify the expression 2(3+y)+4=0 2(3+y) + 4 = 0 .
  • Step 2: Expand to 6+2y+4=0 6 + 2y + 4 = 0 .
  • Step 3: Combine like terms to get 2y+10=0 2y + 10 = 0 .
  • Step 4: Isolate the variable y y . Subtract 10 from both sides: 2y=10 2y = -10 .
  • Step 5: Divide by 2 to solve for y y : y=5 y = -5 .

If y=5 y = -5 , the denominator becomes zero, which makes the original expression undefined.

Therefore, the value of y y must not be 5-5 for the expression to be valid. In conclusion, the restriction on y y is that y5 y \neq -5 .

The correct answer choice is: y5 y \neq -5 .

Answer

y5 y\ne-5

Exercise #9

Determine the area of the domain without solving the expression:

9(4x5x)=20(3x6x+1) 9(4x-\frac{5}{x})=20(3x-\frac{6}{x+1})

Video Solution

Step-by-Step Solution

The domain of the equation is the set of domain values (of the variable in the equation) for which all algebraic expressions in the equation are well defined,

From this, of course - we exclude numbers for which arithmetic operations are not defined,

In the expression on the left side of the given equation:

9(4x5x)=20(3x6x+1) 9(4x-\frac{5}{x})=20(3x-\frac{6}{x+1})

There is a multiplication operation between fractions whose denominators contain algebraic expressions that include the variable of the equation,

These fractions are considered defined as long as the expressions in their denominators are not equal to zero (since division by zero is not possible),

Therefore, the domain of definition of the variable in the equation will be obtained from the requirement that these expressions (in the denominators of the fractions) do not equal zero, as shown below:

For the fraction inside of the parentheses in the expression on the left side we obtain the following:

x0 \boxed{ x\neq0}

For the fraction inside of the parentheses in the expression on the right side we obtain the following:

x+10 x+1\neq0 \\ Proceed to solve the second inequality above (in the same way as solving an equation):

x+10x1 x+1\neq0 \\ \boxed{x\neq-1}

Therefore, the correct answer is answer A.

Note:

It should be noted that the above inequality is a point inequality and not a trend inequality (meaning it negates equality: () (\neq) and does not require a trend: (<,>,\leq,\geq) ) which is solved exactly like solving an equation. This is unlike solving a trend inequality where different solution rules apply depending on the type of expressions in the inequality, for example: solving a first-degree inequality with one variable (which has only first-degree and lower algebraic expressions), is solved almost identically to solving an equation. However any division or multiplication operation of both sides by a negative number requires that the trend be revered.

Answer

x0,x1 x≠0,x≠-1

Exercise #10

Determine the area of the domain without solving the expression:

7x+5=613x \frac{7}{x+5}=\frac{6}{13x}

Video Solution

Step-by-Step Solution

The domain of the equation is the set of domain values (of the variable in the equation) for which all algebraic expressions in the equation are well defined,

From this, of course - we exclude numbers for which arithmetic operations are not defined,

In the expression on the left side of the given equation:

7x+5=613x \frac{7}{x+5}=\frac{6}{13x}

There is a multiplication operation between fractions whose denominators contain algebraic expressions that include the variable of the equation.

These fractions are considered to be defined as long as the expression in their denominators is not equal to zero (given that division by zero is not possible),

Therefore, the domain of definition of the variable in the equation will be obtained from the requirement that these expressions (in the denominators of the fractions) do not equal zero, as follows:

For the fraction in the expression on the left side we obtain:

x+50 x+5\neq0 \\ For the fraction in the expression on the right side we obtain:

13x0 13x\neq0

We will solve these inequalities (in the same way as solving an equation):

x+50x5 x+5\neq0 \\ \boxed{x\neq-5}

13x0/:13x0 13x\neq0 \hspace{8pt}\text{/:13} \\ \boxed{x\neq0}

Therefore, the correct answer is answer A.

Note:

It should be noted that the above inequality is a point inequality and not a directional inequality (meaning it negates equality: () (\neq) and does not require direction: (<,>,\leq,\geq) ) which is solved exactly like solving an equation. This is unlike solving a directional inequality where different solution rules apply depending on the type of expressions in the inequality. For example: solving a first-degree inequality with one variable (which only has first-degree algebraic expressions and below), is solved almost identically to solving an equation. However, any division or multiplication of both sides by a negative number requires reversing the direction.

Answer

x0,x5 x≠0,x≠-5

Exercise #11

15+34:z4y12+8:2=5 \frac{\sqrt{15}+34:z}{4y-12+8:2}=5

What is the field of application of the equation?

Video Solution

Step-by-Step Solution

To solve this problem, we need to identify the values of yy for which the denominator of the expression becomes zero, as these values are not part of the domain.

First, let's simplify the denominator of the given equation:

Original equation: 15+34z4y12+82=5 \frac{\sqrt{15} + \frac{34}{z}}{4y - 12 + \frac{8}{2}} = 5

Simplifying the terms: 34:z remains as it is for simplification purposes, and 82=4 34:z \text{ remains as it is for simplification purposes, and } \frac{8}{2} = 4

Thus, the denominator becomes: (4y12+4)=4y8 (4y - 12 + 4) = 4y - 8

We need to ensure the denominator is not zero to avoid undefined expressions: 4y80 4y - 8 \neq 0

Simplify and solve for yy: 4y80    4y8    y2 4y - 8 \neq 0 \implies 4y \neq 8 \implies y \neq 2

Therefore, the equation is undefined for y=2y = 2, and the answer is that the field of application excludes y=2y = 2.

Given the possible choices for the problem, the correct choice is: y2 y\operatorname{\ne}2

The solution to this problem is y2 y \neq 2 .

Answer

y2 y\operatorname{\ne}2

Exercise #12

22(2x1)=30 22(\frac{2}{x}-1)=30

What is the domain of the equation above?

Video Solution

Answer

x≠0

Exercise #13

2x+6x=18 2x+\frac{6}{x}=18

What is the domain of the above equation?

Video Solution

Answer

x≠0

Exercise #14

2x3=4x 2x-3=\frac{4}{x}

What is the domain of the exercise?

Video Solution

Answer

x≠0

Exercise #15

What is the domain of the exercise?

5x+82x6=30 \frac{5x+8}{2x-6}=30

Video Solution

Answer

x≠3

Topics learned in later sections

  1. Domain of a Function
  2. Indefinite integral