x^2+10x-20=(x^2+2*x*5+25)-25-20=(x+5)^2 - 20
x^2+4x=(x^2+2*x*2+4)-4=(x+2)^2 - 4
x^2-x-6=(x-3)(x+2)
3x^2+9x+6=3(x^2+3x+2)=3(x+1)(x+2)
x^2+10x-20=(x^2+2*x*5+25)-25-20=(x+5)^2 - 20
x^2+4x=(x^2+2*x*2+4)-4=(x+2)^2 - 4
x^2-x-6=(x-3)(x+2)
3x^2+9x+6=3(x^2+3x+2)=3(x+1)(x+2)