Question

What am I doing wrong here?

(5+2x)(9+2x)=221
45+28x+4x^2=221
4x^2+28x=176
4(x^2+7x)=176
4(x^2+7x+49/4)=176+49
4(x+7/2)^2=225
(x+7/2)^2=225/4
x+7/2=±15/4
x=1/4 or x=-29/4

Answer 1

@Chlorophyll

Answer 2

in fifth line

Answer 3

whats wrong with the 5th line?

Answer 4

@satellite73 @phi @UnkleRhaukus

Answer 5

@precal .....c'mon guys its just 'completing the square' ....i cant find what im doing wrong :\