a. x^2+x-2=0
⇔x^2+2x-x-2=0
⇔x(x-1)+2(x-1)=0
⇔\(\left[ \begin{array}{l}x+2=0\\x-1=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=-2\\x=1\end{array} \right.\)
b. (3x-2)-5x(6+2x)=0
⇔3x-2-30x-10x=0
⇔-37x=2
⇔x=$\frac{-2}{37}$
c. 10x+3-5x=4x+12
⇔10x-5x-4x=-3+12
⇔x=9
d. (x^2-4x+4)-25=0
⇔$(x-2)^{2}$ -25=0
⇔(x-2-25)(x-2+25)=0
⇔\(\left[ \begin{array}{l}x-27=0\\x+23=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=27\\x=-23\end{array} \right.\)
