(x^2+x-1)(x+5)
(x^2+x-1)(x)=x^3+x^2-x
(x^2+x-1)(5)= 5x^2+5x-5.
(x^3+x^2-x)+(5x^2+5x-5)=x^3+6x^2+4x-5.
Great explanation DarkBlaze347