-
x^2-11x+18 , -11x = -2x - 9x
x^2-2x-9x+18=0\\\\ x(x-2)-9(x-2)=0\\\\ (x-2)(x-9)=0\\\\ x=2 \ or \ x=9 \\\\ x\in \{2,9\}
-
x^2-6x-9=-5x-3\\\\ x^2-6x-9+5x+3=0 \\\\ x^2-x-6=0 , -x = 2x-3x
x^2+2x-3x-6=0\\\\x(x+2)-3(x+2)=0\\\\ (x+2)(x-3)=0\\\\ x=-2 \ or \ x=3\\\\ x\in \{-2,3\}