2x³+9x²+a = (mx-3) (x+3) ²

(mx-3) (x+3) ² = (mx-3) (x²+6x+9) = mx³+6mx²+9mx-3x²-18x-27=

=mx³+x² (6m-3) + x (9m-18) - 27

mx³=2x³⇒m=2

x² (6m-3) = 9x²⇒6m-3=9⇒6m=12⇒m=2

x (9m-18) = 0⇒9m-18=0⇒9m=18⇒m=2

a=-27

Ответ m=2 a=-27