Question

Determine the maximum of or the minimum value of

y=2x^2+12x

Answer 1

see the almost identical question,

I used completing the square
http://www.jiskha.com/display.cgi?id=1318885052

if you know Calculus, it is easier

y' = 4x+12 = 0 for a max/min
4x = -12
x = -3

then y = 2(9) + 12(-3) = -18

min of -18 when x = -3