[tex]1.\ x^2+5x+4=x^2+x+4x+4=x(x+1)+4(x+1)=(x+1)(x+4)\\\\2.\ x^2-10x+21=x^2-7x-3x+21=x(x-7)-3(x-7)=(x-7)(x-3)\\\\3.\ x^2+2x-63=x^2+9x-7x-63=x(x+9)-7(x+9)=(x+9)(x-7)[/tex] if [tex]x^2+10x+21[/tex] then [tex]=x^2+7x+3x+21=x(x+7)+3(x+7)=(x+7)(x+3)[/tex]
