[tex]2x^2+3x-20=0\\\\2x^2+8x-5x-20=0 \\ \\ 2x(x+4)-5(x+4)=0\\\\(x+4)(2x-5)=0\\\\x+4=0 \ \ or \ \ 2x-5=0 \\\\x=-4 \ \ or \ \ 2x=5 \\\\x=-4 \ \ or \ \ x=\frac{5}{2}[/tex]
[tex]x^2+x-12 = 0\\\\x^2+4x-3x-12 = 0\\\\x(x +4 )-3( x+4) = 0\\\\(x+4)(x-3)=0\\\\x+4=0 \ \ or \ \ x-3=0\\\\x=-4 \ \ or \ \ x=3 [/tex]
