Analyzing the Vertex of y=6x-x²: Maximum or Minimum?

Quadratic Functions with Coefficient Analysis

Does the parable

y=6xx2 y=6x-x^2

Is there a minimum or maximum point?

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Step-by-step video solution

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00:00 Does the parabola have a maximum or minimum point?
00:07 The coefficient A of the function is negative, therefore the parabola is sad
00:11 Therefore the parabola has a maximum point
00:14 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

Does the parable

y=6xx2 y=6x-x^2

Is there a minimum or maximum point?

2

Step-by-step solution

To solve this problem, we need to determine whether the quadratic function y=6xx2 y = 6x - x^2 has a minimum or maximum point.

Firstly, let's identify the general form of the quadratic equation, which is y=ax2+bx+c y = ax^2 + bx + c . For our function, we have:

  • a=1 a = -1
  • b=6 b = 6
  • c=0 c = 0

The coefficient a=1 a = -1 is negative, indicating that the parabola opens downwards. A downward-opening parabola means that the function has a maximum point.

Next, we calculate the x-coordinate of the vertex, which gives the maximum point:

The formula for the x-coordinate of the vertex of a quadratic function ax2+bx+c ax^2 + bx + c is:

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

Substituting the values of a a and b b into the vertex formula, we get:

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

Thus, the x-coordinate of the vertex is x=3 x = 3 . We can substitute this back into the original equation to find the y-coordinate:

y=6(3)(3)2=189=9 y = 6(3) - (3)^2 = 18 - 9 = 9

Therefore, the vertex of the parabola is at (3,9) (3, 9) , and since the parabola opens downwards, this point represents the maximum point of the function.

We conclude that the quadratic function y=6xx2 y = 6x - x^2 reaches a highest point.

3

Final Answer

Highest point

Key Points to Remember

Essential concepts to master this topic
  • Rule: Negative coefficient of x² means parabola opens downward
  • Technique: Find vertex using x=b2a=62(1)=3 x = -\frac{b}{2a} = -\frac{6}{2(-1)} = 3
  • Check: Substitute x = 3: y = 6(3) - 3² = 9 gives maximum ✓

Common Mistakes

Avoid these frequent errors
  • Confusing coefficient signs when determining parabola direction
    Don't look at the b coefficient (6) and think it's positive so the parabola goes up = wrong direction! The b coefficient doesn't determine opening direction. Always check the coefficient of x² (here a = -1) to determine if the parabola opens up (positive a) or down (negative a).

Practice Quiz

Test your knowledge with interactive questions

Identify the coefficients based on the following equation

\( y=x^2 \)

FAQ

Everything you need to know about this question

How do I remember which coefficient determines if it's a maximum or minimum?

+

Look at the coefficient of x² (the 'a' value). Think of it like a smile: positive a = parabola opens up like a smile = minimum point at bottom. Negative a = parabola opens down like a frown = maximum point at top.

Why does the vertex formula work for finding maximum/minimum points?

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The vertex is where the parabola changes direction - it's the turning point. For upward parabolas, this is the lowest point (minimum). For downward parabolas, this is the highest point (maximum).

What if I rewrite the equation in different forms?

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The maximum/minimum nature stays the same! Whether you write y=6xx2 y = 6x - x^2 or y=x2+6x y = -x^2 + 6x , the coefficient of x² is still -1, so it's still a maximum.

How can I double-check my vertex calculation?

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Use the vertex formula x=b2a x = -\frac{b}{2a} , then substitute back. For y=6xx2 y = 6x - x^2 : x = 3, so y = 6(3) - 9 = 9. The vertex (3,9) should be the highest point you can plot.

Can a parabola have both a maximum AND a minimum?

+

No! Each parabola has exactly one vertex - either a maximum OR a minimum, never both. The coefficient of x² determines which one it is.

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