Axis of Symmetry Practice Problems and Solutions

Master finding the axis of symmetry in parabolas with step-by-step practice problems. Learn vertex formula and symmetric points methods with instant feedback.

📚What You'll Master in This Practice Session
  • Apply the vertex formula X = -b/2a to find axis of symmetry
  • Calculate axis of symmetry using two symmetric points on parabolas
  • Identify the vertex and folding line in quadratic functions
  • Solve real-world problems involving parabolic symmetry
  • Convert between different forms of quadratic equations for symmetry
  • Verify axis of symmetry solutions using graphical methods

Understanding Symmetry

Complete explanation with examples

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}

Detailed explanation

Practice Symmetry

Test your knowledge with 4 quizzes

Given the expression of the quadratic function

Finding the symmetry point of the function

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

Examples with solutions for Symmetry

Step-by-step solutions included
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

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)

Video Solution
Exercise #2

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

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

Video Solution
Exercise #3

Given the expression of the quadratic function

Finding the symmetry point of the function

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

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)

Video Solution
Exercise #4

Given the expression of the quadratic function

The symmetrical axis of the expression must be found.

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

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

Video Solution
Exercise #5

Given the expression of the quadratic function

Finding the symmetry point of the function

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

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)

Video Solution

Frequently Asked Questions

What is the axis of symmetry of a parabola?

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The axis of symmetry is a vertical line that passes through the vertex of a parabola, dividing it into two mirror-image halves. If you fold the parabola along this line, both sides would match perfectly.

How do you find the axis of symmetry using the vertex formula?

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Use the formula X = -b/2a where 'a' and 'b' are coefficients from the standard form ax² + bx + c. For example, in x² + 8x + 5, a=1 and b=8, so X = -8/(2×1) = -4.

Can you find axis of symmetry without the vertex formula?

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Yes, you can use two symmetric points on the parabola. The axis of symmetry is the average of their x-coordinates: X = (x₁ + x₂)/2. For points (2,2) and (6,2), the axis is X = (2+6)/2 = 4.

What are the most common mistakes when finding axis of symmetry?

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Common errors include: 1) Forgetting the negative sign in -b/2a, 2) Using wrong coefficients from non-standard form equations, 3) Confusing x and y coordinates when using symmetric points, 4) Not simplifying fractions properly.

Why is the axis of symmetry always a vertical line?

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For standard parabolas (opening up or down), the axis of symmetry is always vertical because parabolas have reflective symmetry across a line parallel to the y-axis. This line passes through the vertex at x = -b/2a.

How do symmetric points help identify the axis of symmetry?

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Symmetric points have the same y-coordinate and are equidistant from the axis of symmetry. The axis lies exactly halfway between these points, making it easy to calculate using the midpoint formula.

What's the difference between vertex and axis of symmetry?

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The vertex is a point (x,y) representing the parabola's minimum or maximum. The axis of symmetry is the vertical line x = h that passes through the vertex, where h is the x-coordinate of the vertex.

Do all parabolas have an axis of symmetry?

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Yes, every parabola has exactly one axis of symmetry. This fundamental property makes parabolas predictable and useful in real-world applications like satellite dishes, bridges, and projectile motion.

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