SOLUTION: Find the maximum value of the function: y=-x^2+8x-4

Algebra.Com
Question 428168: Find the maximum value of the function: y=-x^2+8x-4
Found 2 solutions by solver91311, nerdybill:
Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!


Since the lead coefficient is negative, the parabola opens downward. Therefore, the vertex is a maximum. First find the x-coordinate of the vertex. Take the opposite of the coefficient on the first degree term and divide it by 2 times the lead coefficient. The maximum value of the function is the value of the function at the vertex. Take the x-coordinate you just found and evaluate the function at that x-value.


John

My calculator said it, I believe it, that settles it
The Out Campaign: Scarlet Letter of Atheism
Answer by nerdybill(7384)   (Show Source): You can put this solution on YOUR website!
y=-x^2+8x-4
.
Since the coefficient associated with the x^2 is negative -- we know it is a parabola that opens downwards -- the vertex is then the max.
.
value of x at max is:
x = -b/(2a)
x = -8/(2*(-1))
x = -8/(-2)
x = 4
.
plug above back into:
y=-x^2+8x-4
y=-(4)^2+8(4)-4
y=-(16)+32-4
y=-16+32-4
y = 12 (max value of y)


RELATED QUESTIONS

f(x) = −x^2 + 8x + 3 find the maximum value of the... (answered by stanbon,MathLover1)
Find the maximum y value on the graph of y=f(x)... (answered by reviewermath,stanbon)
If y = -4 sin (x/2) + 6. What is the maximum value of the... (answered by Cromlix)
Find the maximum value of the function:... (answered by stanbon)
Find the vertex, the line of symmetry, the maximum or minimum value of the quadratic... (answered by solver91311)
Find the vertex, the line of symmetry, the maximum or minimum value of the quadratic... (answered by richard1234)
Find the vertex, the line of symmetry, the maximum or minimum value of the quadratic... (answered by ewatrrr)
Find the vertex, the line of symmetry, the maximum or minimum value of the quadratic... (answered by solver91311)
Find the vertex, the line of symmetry, the maximum or minimum value of the quadratic... (answered by Fombitz)