Respuesta :

distributive property
a(b+c)=ab+ac
lets say that the (x²+3x+4) is the a
(x²+3x+4)=(x-5)=(x²+3x+4)(x)+(x²+3x+4)(-5)
distribute further
x³+3x²+4x-5x²-15x-20
x³-2x-11x-20