Find the maximum or minimum of the following quadratic function: y = x2 - x - 56.
A. -56
B. 56
C. -225/4
D. 225/4

Question

Find the maximum or minimum of the following quadratic function: y = x2 - x - 56.
	A.	-56
	B.	56
	C.	-225/4
	D.	225/4

campbell_st · Answer

the maximum of minimum for a quadratic lies on the line of symmetry... 

your parabola is concave up... so its a minimum value 

so for any quadratic 

$$ax^2 + bx + c$$

the line of symmetry is 

$$x = \frac{-b}{2 \times a}$$

in your question b = -1 and a = 1 

so substitute them into the line of symmetry formula

when you get the value, substitute it into the original equation to get the minimum value