Đáp án:
$a)(x+1)(x+2)-(x+3)(x-3)=0$
$⇔x^2+2x+x+2-(x^2-9)=0$
$⇔x^2+3x+2-x^2+9=0$
$⇔3x+11=0$
$⇔x=\dfrac{-11}{3}$
$b)(x+3)^2-(x+1)(x-1)=0$
$⇔x^2+6x+9-(x^2-1)=0$
$⇔x^2+6x+9-x^2+1=0$
$⇔6x+10=0$
$⇔x=\dfrac{-5}{3}$
$c)(x-3)^2-(x-2)(x+2)=0$
$⇔x^2-6x+9-(x^2-4)=0$
$⇔x^2-6x+9-x^2+4=0$
$⇔-6x+13=0$
$⇔x=\dfrac{13}{6}$
$d)(x+4)(x-4)-(x+2)^2=0$
$⇔x^2-16-(x^2+4x+4)=0$
$⇔x^2-16-x^2-4x-4=0$
$⇔-4x-20=0$
$⇔x=-5$
$e)(x+5)(5-x)+(x-1)^2=0$
$⇔25-x^2+x^2-2x+1=0$
$⇔-2x+26=0$
$⇔x=13$
$f)(2x-3)(2x+3)-(x-1)^2-3x(x-5)=-44$
$⇔4x^2-9-(x^2-2x+1)-(3x^2-15x)=-44$
$⇔4x^2-9-x^2+2x-1-3x^2+15x+44=0$
$⇔17x+34=0$
$⇔x=-2$
$g)(5x+1)^2-(5x+3)(5x-3)=30$
$⇔25x^2+10x+1-(25x^2-9)=30$
$⇔25x^2+10x+1-25x^2+9=30$
$⇔10x+10=30$
$⇔x=2$
$h)(x+3)^2+(x-2)(x+2)-2(x-1)^2=7$
$⇔x^2+6x+9+x^2-4-2(x^2-2x+1)=7$
$⇔2x^2+6x+5-2x^2+4x-2=7$
$⇔10x+3=7$
$⇔10x=4$
$⇔x=\dfrac{2}{5}$
