20
e)(2x+1)²-2(x+4)=(2x-1)²+3(x+2)+7=
(4x²+4x+1)-2x-8=(4x²-4x+1)+3x+6+7⇒
4x²+4x+1-2x-8=4x²-4x+1+3x+13⇒
4x²+2x-7=4x²-x+14⇒
4x²-4x²+2x+x-7-14=0
3x-21=0⇒3x=21⇒x=21/3⇒x=7
f)(x+5)²+(x-6)(x+6)=2(x+3)²+15=
(x²+10x+25)+(x²-36)=2(x²+6x+9)+15⇒
x²+10x+25+x²-36=2x²+12x+18+15=
2x²+10x-11=2x²+12x+33
2x²-2x²+10x-12x-11-33=0
-2x-44=0⇒-2x=44⇒x=44/-2⇒x=-22
sucees
