Symmetry: Finding a stationary point

Examples with solutions for Symmetry: Finding a stationary point

Exercise #1

Given the expression of the quadratic function

Finding the symmetry point of the function

f(x)=12x2 f(x)=\frac{1}{2}x^2

Video Solution

Step-by-Step Solution

To determine the symmetry (vertex) point of the quadratic function f(x)=12x2 f(x) = \frac{1}{2}x^2 , we will use the formula for the x-coordinate of the vertex (or axis of symmetry) for a general quadratic function f(x)=ax2+bx+c f(x) = ax^2 + bx + c , which is given by:

  • x=b2a x = -\frac{b}{2a}

In this problem, the coefficients are a=12 a = \frac{1}{2} , b=0 b = 0 , and c=0 c = 0 . By substituting these values into the vertex formula:

x=02×12=0 x = -\frac{0}{2 \times \frac{1}{2}} = 0

This tells us that the x-coordinate of the vertex is 0 0 . To find the y-coordinate of the vertex, we substitute x=0 x = 0 back into the function f(x)=12(x2) f(x) = \frac{1}{2}(x^2) :

f(0)=12(0)2=0 f(0) = \frac{1}{2}(0)^2 = 0

Thus, the vertex of the function, also its symmetry point, is at the coordinate (0,0) (0,0) .

Therefore, the symmetry point of the function f(x)=12x2 f(x) = \frac{1}{2}x^2 is (0,0) (0, 0) .

Answer

(0,0) (0,0)

Exercise #2

Given the expression of the quadratic function

Finding the symmetry point of the function

f(x)=2x2 f(x)=2x^2

Video Solution

Step-by-Step Solution

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

  • Identify the coefficients of the quadratic function.
  • Apply the vertex formula to find the axis of symmetry and subsequently the vertex.
  • Calculate the function's value at the symmetry point.

Now, let's work through each step:
Step 1: The given function is f(x)=2x2 f(x) = 2x^2 , where a=2 a = 2 and b=0 b = 0 .
Step 2: The axis of symmetry for a quadratic function in the form ax2+bx+c ax^2 + bx + c is given by x=b2a x = -\frac{b}{2a} . With b=0 b = 0 , this simplifies to x=0 x = 0 .
Step 3: To find the vertex, calculate the function's value at x=0 x = 0 , using f(x)=2x2 f(x) = 2x^2 .
Plugging in x=0 x = 0 , we find:
f(0)=2(0)2=0 f(0) = 2(0)^2 = 0 .
Thus, the vertex, and hence the symmetry point of the function, is (0,0) (0, 0) .

Therefore, the solution to the problem is (0,0) (0, 0) .

Answer

(0,0) (0,0)

Exercise #3

Given the expression of the quadratic function

Finding the symmetry point of the function

f(x)=5x2+10 f(x)=-5x^2+10

Video Solution

Step-by-Step Solution

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

  • Step 1: Identify the coefficients a a , b b , and c c from the quadratic function.
  • Step 2: Apply the vertex formula to find the x-coordinate of the symmetry point.
  • Step 3: Substitute the x-coordinate back into f(x) f(x) to find the y-coordinate of the vertex.
  • Step 4: Conclude the symmetry point as the vertex, (x,f(x))(x, f(x)).

Now, let's work through each step:

Step 1: The quadratic function is f(x)=5x2+10 f(x) = -5x^2 + 10 . The coefficients are a=5 a = -5 , b=0 b = 0 , and c=10 c = 10 .

Step 2: Applying the vertex formula x=b2a x = -\frac{b}{2a} , we have:

x=02(5)=0 x = -\frac{0}{2(-5)} = 0 .

Step 3: Substitute x=0 x = 0 back into the function:

f(0)=5(0)2+10=10 f(0) = -5(0)^2 + 10 = 10 .

Step 4: Therefore, the vertex and symmetry point of the function is (0,10)(0, 10).

The correct choice from the given options is (0,10)(0,10).

Therefore, the solution to the problem is (0,10) (0,10) .

Answer

(0,10) (0,10)

Exercise #4

Given the expression of the quadratic function

Finding the symmetry point of the function

f(x)=35x2 f(x)=3-5x^2

Video Solution

Step-by-Step Solution

To find the symmetry point of the quadratic function f(x)=35x2 f(x) = 3 - 5x^2 , we follow these steps:

  • Identify that the function is in the form f(x)=ax2+bx+c f(x) = ax^2 + bx + c , where a=5 a = -5 , b=0 b = 0 , and c=3 c = 3 .

  • The x-coordinate of the symmetry point, also known as the vertex, is given by the formula x=b2a x = -\frac{b}{2a} .

  • Substitute the values: x=02(5)=0 x = -\frac{0}{2(-5)} = 0 .

  • Calculate the y-coordinate by substituting x=0 x = 0 into the function: f(0)=35(0)2=3 f(0) = 3 - 5(0)^2 = 3 .

  • Hence, the symmetry point of the function is (0,3) (0, 3) .

Therefore, the symmetry point of the function f(x)=35x2 f(x) = 3 - 5x^2 is (0,3) (0, 3) .

Answer

(0,3) (0,3)

Exercise #5

Given the expression of the quadratic function

Finding the symmetry point of the function

f(x)=3x2+6x f(x)=3x^2+6x

Video Solution

Step-by-Step Solution

To find the symmetry point of the quadratic function f(x)=3x2+6x f(x) = 3x^2 + 6x , follow these steps:

  • Step 1: Identify the coefficients from the quadratic function ax2+bx+c ax^2 + bx + c . Here, a=3 a = 3 and b=6 b = 6 .
  • Step 2: Use the vertex formula for the symmetry point, which is given by x=b2a x = -\frac{b}{2a} .
  • Step 3: Substitute the values of a a and b b into the formula:

x=62×3=66=1 x = -\frac{6}{2 \times 3} = -\frac{6}{6} = -1

  • Step 4: Substitute x=1 x = -1 back into the original function to find the corresponding y y -coordinate:

f(1)=3(1)2+6(1)=3×16=36=3 f(-1) = 3(-1)^2 + 6(-1) = 3 \times 1 - 6 = 3 - 6 = -3

  • Step 5: Therefore, the symmetry point of the function is (1,3)(-1, -3).

Thus, the symmetry point of the given quadratic function f(x)=3x2+6x f(x) = 3x^2 + 6x is (1,3)\boxed{(-1, -3)}.

Answer

(1,3) (-1,-3)

Exercise #6

Given the expression of the quadratic function

Finding the symmetry point of the function

f(x)=3+3x2 f(x)=3+3x^2

Video Solution

Step-by-Step Solution

To solve this problem, we need to find the symmetry point of the quadratic function given by f(x)=3+3x2 f(x) = 3 + 3x^2 .

  • Step 1: Identify the type of quadratic equation. Here, it's ax2+bx+c ax^2 + bx + c where a=3 a = 3 , b=0 b = 0 , and c=3 c = 3 .
  • Step 2: Use the formula for the symmetry point x=b2a x = -\frac{b}{2a} . Since b=0 b = 0 , the formula simplifies to x=0 x = 0 .
  • Step 3: Calculate the y-coordinate by substituting x=0 x = 0 into the original function: f(0)=3(0)2+3=3 f(0) = 3(0)^2 + 3 = 3 .

Thus, the symmetry point (also the vertex of the parabola) is (0,3) (0, 3) .

Therefore, the solution to the problem is (0,3) (0, 3) .

Answer

(0,3) (0,3)

Exercise #7

Given the expression of the quadratic function

Finding the symmetry point of the function

f(x)=4x2+8x+3 f(x)=-4x^2+8x+3

Video Solution

Step-by-Step Solution

To find the symmetry point of the quadratic function f(x)=4x2+8x+3 f(x) = -4x^2 + 8x + 3 , follow these steps:

  • Step 1: Identify key parameters
    The function is of the form f(x)=ax2+bx+c f(x) = ax^2 + bx + c , with a=4 a = -4 , b=8 b = 8 , and c=3 c = 3 .
  • Step 2: Find the x-coordinate of the vertex
    Use the formula for the x-coordinate of the vertex: x=b2a x = -\frac{b}{2a} .
    Substitute the values for b b and a a :
    x=82×4=88=1 x = -\frac{8}{2 \times -4} = -\frac{8}{-8} = 1 .
  • Step 3: Find the y-coordinate by substituting back into f(x) f(x)
    Calculate f(1) f(1) :
    f(1)=4(1)2+8(1)+3=4+8+3=7 f(1) = -4(1)^2 + 8(1) + 3 = -4 + 8 + 3 = 7 .
  • Step 4: State the symmetry point
    The symmetry point, or vertex, of the function is (1,7) (1, 7) .

Therefore, the symmetry point of the quadratic function f(x)=4x2+8x+3 f(x) = -4x^2 + 8x + 3 is (1,7)(1, 7).

Answer

(1,7) (1,7)

Exercise #8

Given the expression of the quadratic function

Finding the symmetry point of the function

f(x)=5xx2 f(x)=5x-x^2

Video Solution

Step-by-Step Solution

To find the symmetry point of the quadratic function f(x)=5xx2 f(x) = 5x - x^2 , we will determine the vertex of the parabola.

  • Step 1: Express the quadratic function in standard form:
    The given function is already in standard form: f(x)=x2+5x f(x) = -x^2 + 5x , where a=1 a = -1 and b=5 b = 5 .

  • Step 2: Apply the vertex formula to find the x-coordinate of the vertex:
    For the quadratic function ax2+bx+c ax^2 + bx + c , the x-coordinate of the vertex is found using x=b2a x = -\frac{b}{2a} .

  • Step 3: Calculate the x-coordinate:
    xamp;=52×(1)amp;=52amp;=52 \begin{aligned} x &= -\frac{5}{2 \times (-1)} \\ &= -\frac{5}{-2} \\ &= \frac{5}{2} \end{aligned}

  • Step 4: Substitute x=52 x = \frac{5}{2} back into the function to find the y-coordinate:
    f(52)amp;=(52)2+5(52)amp;=254+252amp;=254+504amp;=254 \begin{aligned} f\left(\frac{5}{2}\right) &= -\left(\frac{5}{2}\right)^2 + 5\left(\frac{5}{2}\right) \\ &= -\frac{25}{4} + \frac{25}{2} \\ &= -\frac{25}{4} + \frac{50}{4} \\ &= \frac{25}{4} \end{aligned}

  • Step 5: Determine the symmetry point:
    The symmetry point, and thus the vertex of the function, is (52,254)\left(\frac{5}{2}, \frac{25}{4}\right), or (212,614) (2\frac{1}{2}, 6\frac{1}{4}) .

Therefore, the symmetry point of the function is (212,614)(2\frac{1}{2}, 6\frac{1}{4}).

Answer

(212,614) (2\frac{1}{2},6\frac{1}{4})

Exercise #9

Given the expression of the quadratic function

Finding the symmetry point of the function

f(x)=6x2+24x f(x)=-6x^2+24x

Video Solution

Step-by-Step Solution

To solve this problem, we'll find the vertex of the quadratic function f(x)=6x2+24x f(x) = -6x^2 + 24x .

  • Step 1: Identify the coefficients from the quadratic function.
  • Step 2: Use the vertex formula to find the x-coordinate.
  • Step 3: Substitute the x-coordinate back into the function to find the y-coordinate.

Now, let's work through each step:
Step 1: The function given is f(x)=6x2+24x f(x) = -6x^2 + 24x . Here, a=6 a = -6 and b=24 b = 24 .
Step 2: Use the vertex formula x=b2a x = -\frac{b}{2a} . Substituting the values, we get x=242(6)=2412=2 x = -\frac{24}{2 \cdot (-6)} = \frac{24}{12} = 2 .
Step 3: Substitute x=2 x = 2 back into the function to find the y-coordinate: f(2)=6(2)2+242=24+48=24 f(2) = -6(2)^2 + 24 \cdot 2 = -24 + 48 = 24 .

Therefore, the symmetry point of the function is (2,24) (2, 24) .

Answer

(2,24) (2,24)

Exercise #10

Given the expression of the quadratic function

Finding the symmetry point of the function

f(x)=3x2+12 f(x)=-3x^2+12

Video Solution

Step-by-Step Solution

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

  • Step 1: Identify the given coefficients from f(x)=ax2+bx+c f(x) = ax^2 + bx + c : a=3 a = -3 , b=0 b = 0 , and c=12 c = 12 .
  • Step 2: Apply the vertex formula x=b2a x = -\frac{b}{2a} to find the x-coordinate of the vertex.
  • Step 3: Plug the x-coordinate back into the function to find the y-coordinate.

Now, let's work through each step:
Step 1: The function is given as f(x)=3x2+12 f(x) = -3x^2 + 12 . We have a=3 a = -3 , b=0 b = 0 , and c=12 c = 12 .
Step 2: Using the formula x=b2a x = -\frac{b}{2a} , substitute b=0 b = 0 and a=3 a = -3 :
x=02×3=0 x = -\frac{0}{2 \times -3} = 0
Step 3: Substitute x=0 x = 0 back into the quadratic function to find the y-coordinate:
f(0)=3(0)2+12=12 f(0) = -3(0)^2 + 12 = 12
So, the vertex, or symmetry point, of the function is (0,12) (0, 12) .

Therefore, the solution to the problem is (0,12) (0, 12) .

Answer

(0,12) (0,12)