Question

Help just help please. !!!

Answer 1

Answer: The  maximum   value is   -3.75  

Note: -3.75 = -15/4

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Explanation:

The given quadratic is in the form y = ax^2 + bx + c, where,

• a = -1
• b = 1
• c = -4

We'll plug the values of 'a' and b into the formula below

h = -b/(2a)

h = -1/(2(-1))

h = 1/2

h = 0.5

This represents the x coordinate of the vertex. Recall the vertex is (h,k).

Plug this x value into the function to find its corresponding y coordinate

y = -x^2 + x - 4

y = -(0.5)^2 + 0.5 - 4

y = -3.75

The vertex is located at (0.5, -3.75)

Since a < 0, this means the parabola opens downward and that the vertex is the highest point on the parabola. Therefore, the largest y can get is y = -3.75 which we consider the maximum.

The graph visually helps confirm this (see image attachment).

Side note: -3.75 = -15/4

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Here's another way we can find the vertex (h,k). We'll complete the square to get the function into vertex form

y = -x^2 + x - 4

y + 4 = -x^2 + x

y + 4 = -(x^2 - x)

y + 4 = -(x^2 - x + 0)

y + 4 = -(x^2 - x + 0.25 - 0.25) .... see note below

y + 4 = -(x^2 - x + 0.25) -(-0.25)

y + 4 = -(x^2 - x + 0.25) + 0.25

y + 4 = -(x - 0.5)^2 + 0.25

y = -(x - 0.5)^2 + 0.25 - 4

y = -(x - 0.5)^2 - 3.75

This is in the form y = a(x-h)^2 + k where (h,k) = (0.5, -3.75).

Note: The x coefficient is -1 which cuts in half to -0.5, then that squares to 0.25