Symmetry in a parabola

🏆Practice symmetry

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}

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Test yourself on symmetry!

einstein

Given the expression of the quadratic function

The symmetrical axis of the expression must be found.

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

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Let's look at an example

First method: Solve for X at the vertex based on the formula.

Given the function x2+8x+5x^2+8x+5
Let's plug it into the formula and we will get:
x=821=81=8x=-\frac{8}{2\cdot1}=-\frac{8}{1}=-8
From this it follows that, the axis of symmetry is X=8X=-8


Second method: Find the axis of symmetry based on symmetrical points.

Given the points (2,2)(2,2),(6,2)(6,2)

Let's plug them into the formula and we will get:
x=6+22=82=4x=\frac{6+2}{2}=\frac{8}{2}=4
The axis of symmetry is X=4X=4


If you are interested in this article, you might also be interested in the following articles:

Symmetry in Trapezoids

Rotational Symmetry in Parallelograms

Symmetry of the Rhombus

In the Tutorela blog, you will find a variety of articles on mathematics.


Examples and exercises with solutions on 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)

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