Respuesta :

-3b^2 +15b +18 = - (3b^2 -15b -18) = - (3b^2 - 3*5b -3*6) = - 3(b^2 -5b -6) =

= - 3(b*b -2b-3b -2*3) = - 3[b(b-2) -3(b-2)] = - 3(b-2)(b-3)

hope this will help you and will be understand it right easy