Posted by **drew** on Monday, February 4, 2013 at 6:11pm.

Find the maximum or minimum of the following quadratic function: y = x2 - x - 56.

A. -56

B. 56

C. -225/4

D. 225/4

d

- algebra -
**Me**, Monday, February 4, 2013 at 6:16pm
1. y=x2 - 16

for maximum or minumum, dy/dx=0

hence 2x=0 or x=0

minimum value of function occurs when x=0 which is y=-16

2.using same principle as above,

dy/dx=10x+5

when dy/dx=0 => 10x+5=0 => x=-1/2

minimum value of y= -5/4 - 5/2 + 11

for 3, 4 and 5 use the same principle as 1 and 2

- algebra -
**bobpursley**, Monday, February 4, 2013 at 6:19pm
max: infinity (at x=inf)

min: x=1/2, y= you figure it. check sign.

- algebra -
**Reiny**, Monday, February 4, 2013 at 6:37pm
Not sure if you know Calculus, as done by Me

so let's complete the square

y = x^2 - x - 56

= x^2 - x + 1/4 - 1/4 - 56

= (x- 1/2)^2 - 225/4

so we have a min of -225/4 , when x = 1/2

(min because the parabola opens upwards)

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