1) 18x+9x^2 = 9x(2+x)
2) x(x-4)-5(x-4) = (x-4)(x-5)
3) 5(x-5)-2x(-5+x) = 5(x-5)-2x(x-5) = (x-5)(5-2x)
4) 5(x-7)+x(7-x) = 5(x-7)-x(x-7) = (x-7)(5-x)
1) 18x+9x^2 = 9x(2+x)
2) x(x-4)-5(x-4) = (x-4)(x-5)
3) 5(x-5)-2x(-5+x) = 5(x-5)-2x(x-5) = (x-5)(5-2x)
4) 5(x-7)+x(7-x) = 5(x-7)-x(x-7) = (x-7)(5-x)