Symmetry - Examples, Exercises and Solutions

The axis of symmetry in a parabola is the axis that passes through its vertex in such a way that if we folded the right side over the left side, both sides would appear joined.
Let's see it in an illustration:

Symmetry 1

To find the axis of symmetry, we must locate the value of X X of the vertex of the parabola or do it through the parabola's vertex formula or with the help of two symmetric points on the parabola.

Vertex Formula of the Parabola

X=b2a X=\frac{-b}{2a}

Formula for two symmetric points:

B3 - The formula to find X a vertex using two symmetric points

XVertex=The value of X at the first point + The value of X at the second point2 X_{Vertex}=\frac{The~value~of~X~at~the~first~point~+~The~value~of~X~at~the~second~point}{2}

Suggested Topics to Practice in Advance

  1. The quadratic function
  2. Parabola
  3. Plotting the Quadratic Function Using Parameters a, b and c
  4. Finding the Zeros of a Parabola
  5. Positive and Negative intervals of a Quadratic Function
  6. Increasing and Decreasing Intervals of a Parabola
  7. Vertex of a parabola

Practice Symmetry

Examples with solutions for Symmetry

Exercise #1

Given the expression of the quadratic function

The symmetrical axis of the expression must be found.

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

Video Solution

Step-by-Step Solution

To find the axis of symmetry for the quadratic function f(x)=3x2+3 f(x) = -3x^2 + 3 , we follow these steps:

  • Identify coefficients: Here, a=3 a = -3 , b=0 b = 0 , and c=3 c = 3 .
  • Use the axis of symmetry formula for a quadratic ax2+bx+c ax^2 + bx + c given by x=b2a x = -\frac{b}{2a} .
  • Substitute b=0 b = 0 and a=3 a = -3 into the formula: x=02×(3) x = -\frac{0}{2 \times (-3)} .
  • This simplifies to x=0 x = 0 .

The axis of symmetry for the quadratic function f(x)=3x2+3 f(x) = -3x^2 + 3 is therefore x=0 x = 0 .

Answer

x=0 x=0

Exercise #2

Given the expression of the quadratic function

The symmetrical axis of the expression must be found.

f(x)=7x2 f(x)=7x^2

Video Solution

Step-by-Step Solution

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

  • Step 1: Identify the coefficients in the quadratic equation.
  • Step 2: Apply the formula for the axis of symmetry.
  • Step 3: Substitute the coefficients into the formula and solve.

Now, let's work through each step:
Step 1: The quadratic function given is f(x)=7x2 f(x) = 7x^2 which can be written in the form ax2+bx+c ax^2 + bx + c . Here, a=7 a = 7 , b=0 b = 0 , and c=0 c = 0 .
Step 2: We'll use the formula for the axis of symmetry: x=b2a x = -\frac{b}{2a} .
Step 3: Substitute a=7 a = 7 and b=0 b = 0 in the formula:
x=02×7=0 x = -\frac{0}{2 \times 7} = 0 Therefore, the axis of symmetry for the quadratic function f(x)=7x2 f(x) = 7x^2 is x=0 x = 0 .

Therefore, the solution to the problem is x=0 x = 0 , corresponding to choice #3.

Answer

x=0 x=0

Exercise #3

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 #4

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 #5

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 #6

Given the expression of the quadratic function

The symmetrical axis of the expression must be found.

f(x)=4x2+6 f(x)=4x^2+6

Video Solution

Step-by-Step Solution

To find the axis of symmetry for the quadratic function f(x)=4x2+6 f(x) = 4x^2 + 6 , we employ the formula for the axis of symmetry of a parabola given by ax2+bx+c ax^2 + bx + c , which is x=b2a x = -\frac{b}{2a} .

Given f(x)=4x2+0x+6 f(x) = 4x^2 + 0x + 6 , we identify the coefficients from the function:

  • a=4 a = 4
  • b=0 b = 0

Substituting these values into the formula:

x=b2a=02×4=0 x = -\frac{b}{2a} = -\frac{0}{2 \times 4} = 0

Thus, the axis of symmetry for the quadratic function is x=0 x = 0 .

Therefore, the solution to the problem is x=0\mathbf{x = 0}.

Answer

x=0 x=0

Exercise #7

A quadratic equation is graphed below.

What is the axis of symmetry for the graph f(x)=3x2+2 f(x)=3x^2+2 ?

222

Video Solution

Step-by-Step Solution

To determine the axis of symmetry for the function f(x)=3x2+2 f(x) = 3x^2 + 2 , we follow these steps:

  • Identify the coefficients from the function. Here, a=3 a = 3 and b=0 b = 0 . The constant term c=2 c = 2 does not affect the axis of symmetry.
  • Use the axis of symmetry formula for a quadratic function: x=b2a x = -\frac{b}{2a} .
  • Substitute the values for b b and a a into the formula: x=02×3=0 x = -\frac{0}{2 \times 3} = 0 .

This calculation shows that the axis of symmetry for the graph of the quadratic function is x=0 x = 0 .

Thus, the solution to the problem is that the axis of symmetry is x=0 x = 0 .

Answer

x=0 x=0

Exercise #8

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 #9

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 #10

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 #11

Given the expression of the quadratic function

The symmetrical axis of the expression must be found.

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

Video Solution

Step-by-Step Solution

To solve this problem, we'll apply the formula for the axis of symmetry of a quadratic function:

  • Step 1: Recognize the function is f(x)=2x2+8x+4 f(x) = 2x^2 + 8x + 4 .
  • Step 2: Identify the coefficients: a=2 a = 2 and b=8 b = 8 .
  • Step 3: Use the axis of symmetry formula x=b2a x = -\frac{b}{2a} .

Now, substituting the values of a a and b b into the formula:
x=82×2 x = -\frac{8}{2 \times 2} ,
x=84 x = -\frac{8}{4} ,
x=2 x = -2 .

Therefore, the axis of symmetry for the given quadratic function is x=2 x = -2 .

Answer

x=2 x=-2

Exercise #12

Given the expression of the quadratic function

The symmetrical axis of the expression must be found.

f(x)=2x2+16 f(x)=-2x^2+16

Video Solution

Step-by-Step Solution

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

  • Step 1: Identify the coefficients a a and b b .
  • Step 2: Apply the symmetry axis formula.
  • Step 3: Simplify the expression to find the solution.

Now, let's work through each step:

Step 1: From the quadratic function f(x)=2x2+16 f(x) = -2x^2 + 16 , we identify the coefficients: a=2 a = -2 and b=0 b = 0 .

Step 2: Using the formula for the axis of symmetry, x=b2a x = -\frac{b}{2a} , we substitute the identified coefficients:

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

Step 3: Simplifying the expression, we have:

x=0 x = 0 .

Therefore, the solution to the problem is the axis of symmetry: x=0 x = 0 .

Answer

x=0 x=0

Exercise #13

Calculate the axis of symmetry of the quadratic function below:

f(x)=3x2+6x6 f(x)=3x^2+6x-6

Video Solution

Step-by-Step Solution

To find the axis of symmetry for the quadratic function f(x)=3x2+6x6 f(x) = 3x^2 + 6x - 6 , we begin by identifying the coefficients in the general form of a quadratic equation: ax2+bx+c ax^2 + bx + c . Here, a=3 a = 3 , b=6 b = 6 , and c=6 c = -6 .

The formula for the axis of symmetry of a quadratic function is:

x=b2a x = -\frac{b}{2a} .

Substituting the given values into the formula, we have:

x=623 x = -\frac{6}{2 \cdot 3} .

Calculating the above expression, we get:

x=66=1 x = -\frac{6}{6} = -1 .

Thus, the axis of symmetry for this quadratic function is x=1 x = -1 .

Therefore, the solution to the problem is x=1 x = -1 .

Answer

x=1 x=-1

Exercise #14

A quadratic function is graphed below.

What is the axis of symmetry for the graph f(x)=x2+4x f(x)=x^2+4x ?

Video Solution

Step-by-Step Solution

To solve this problem, we'll determine the axis of symmetry using the appropriate formula:

  • Step 1: Identify the coefficients a a , b b , and c c
  • Step 2: Use the axis of symmetry formula
  • Step 3: Substitute the values and solve

Now, let's work through each step:

Step 1: The quadratic function is f(x)=x2+4x f(x) = x^2 + 4x . Here, a=1 a = 1 , b=4 b = 4 , and c=0 c = 0 .

Step 2: Use the axis of symmetry formula x=b2a x = -\frac{b}{2a} .

Step 3: Substitute the values: x=42×1=42=2 x = -\frac{4}{2 \times 1} = -\frac{4}{2} = -2

Therefore, the axis of symmetry for the graph is x=2 x = -2 .

Answer

x=2 x=-2

Exercise #15

Given the expression of the quadratic function

The symmetrical axis of the expression must be found.

f(x)=x2+4x+1 f(x)=x^2+4x+1

Video Solution

Step-by-Step Solution

To solve this problem, we'll apply the formula for finding the axis of symmetry for a quadratic function:

  • Step 1: Identify the coefficients.
    For the quadratic function f(x)=x2+4x+1 f(x) = x^2 + 4x + 1 , we have a=1 a = 1 and b=4 b = 4 .
  • Step 2: Use the formula for the axis of symmetry.
    The axis of symmetry for a quadratic function ax2+bx+c ax^2 + bx + c is given by x=b2a x = -\frac{b}{2a} .
  • Step 3: Substitute the values of a a and b b into the formula.
    Substitute b=4 b = 4 and a=1 a = 1 to get: x=42×1 x = -\frac{4}{2 \times 1} .
  • Step 4: Simplify to find the value of x x .
    This simplifies to x=42=2 x = -\frac{4}{2} = -2 .

Therefore, the axis of symmetry for the given quadratic function is x=2 x = -2 .

Answer

x=2 x=-2