If y = x2 + bx + c then to complete the square you add and subtract which one of the following values?

Question

Can someone help me with this I don't really understand the question. Thank You!
A. b/2
B. b/c
C.(b/2)^2
D.√(b/2)
E. None of the above

Answer 1

look at a specific example first

 

x^2+6x-7=0

x^2+6x   =7

(6/2)^2=3^2=9

x^2+6x+9=7+9

(x+3)^2=16

x+3=4

x+3=-4

x=1 and x=-7

 

x^2+bx+c=0

(b/2)^2 which is C.