Resposta:
a) (x+2)*(x-3)
x^2-3x+2x -6
x^2 -x-6
-------------------
b) (x+y+1).(x+4)
x^2+4x +xy+4y +x +4
x^2+5x+xy+ 4y+4
----------------------------
c) x*(x+y-3)
x^2+xy-3x
d) (x^2+6).(x-4)
x^3-4x^2+6x-24
