Calculate the Vertex of the Quadratic Function: f(x) = -6x^2 + 24x

Quadratic Vertex with Vertex Formula

Given the expression of the quadratic function

Finding the symmetry point of the function

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

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the point of symmetry in the function
00:03 The point of symmetry is the point where if you fold the parabola in half
00:06 The halves will be equal to each other
00:09 Let's examine the function's coefficients
00:12 We'll use the formula to calculate the vertex point
00:16 We'll substitute appropriate values according to the given data and solve for X at the point
00:27 This is the X value at the point of symmetry
00:30 Now we'll substitute this X value in the function to find the Y value at the point
00:45 This is the Y value at the point of symmetry
00:53 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Given the expression of the quadratic function

Finding the symmetry point of the function

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

2

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) .

3

Final Answer

(2,24) (2,24)

Key Points to Remember

Essential concepts to master this topic
  • Vertex Formula: Use x=b2a x = -\frac{b}{2a} to find x-coordinate
  • Technique: For f(x)=6x2+24x f(x) = -6x^2 + 24x , x = -24/(2(-6)) = 2
  • Check: Substitute x = 2: f(2) = -6(4) + 48 = 24 ✓

Common Mistakes

Avoid these frequent errors
  • Forgetting to substitute x-coordinate back into the function
    Don't stop after finding x = 2 and guess the y-coordinate = incomplete vertex! The y-coordinate requires calculation by substituting x back into the original function. Always substitute x = 2 into f(x) = -6x² + 24x to get f(2) = 24.

Practice Quiz

Test your knowledge with interactive questions

Given the expression of the quadratic function

Finding the symmetry point of the function

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

FAQ

Everything you need to know about this question

Why do I use -b/2a instead of completing the square?

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The vertex formula x=b2a x = -\frac{b}{2a} is a shortcut derived from completing the square! It's faster and reduces calculation errors, especially when dealing with larger coefficients like -6 and 24.

What if my quadratic doesn't have a c term?

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That's perfectly fine! When c = 0 (like in our example), you still use the same vertex formula. The missing constant term doesn't affect finding the x-coordinate of the vertex.

How do I know if the vertex is a maximum or minimum?

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Look at the coefficient of x². If a is negative (like -6), the parabola opens downward, so the vertex is a maximum. If a is positive, it's a minimum.

Can I factor this function to find the vertex?

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You could factor f(x) = -6x² + 24x = -6x(x - 4), but this gives you the x-intercepts (0 and 4), not the vertex. The vertex formula is more direct for finding the turning point.

What does the vertex represent in real life?

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The vertex shows the optimal point - like maximum profit, highest point of a ball's path, or minimum cost. Since our parabola opens down, (2, 24) represents the maximum value.

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