If (2x+3y)2=130 and xy=6, find the value of 4x2+9y2
58
62
59
57
Using (a+b)2=a2+b2+2ab, we get
(2x+3y)2=(2x)2+(3y)2+2×2x×3y
⇒130=4x2+9y2+12xy
⇒130=4x2+9y2+12×6
⇒130=4x2+9y2+72
⇒4x2+9y2=130−72=58
If 2x+3y=8 and xy=2, find the value of 4x2+9y2.