### Instruction: Completely factor the following expression: \[(15x^3+80x-5)-(-4x^3+4x-5).\].### Response: Ok, so let's first add together the two expressions in the parentheses.
Right. So we get $15x^3+80x-5+4x^3-4x+5$ which simplifies to $19x^3+76x$.
Exactly. So now we can factor $19x$ out of the expression to get $19x(x^2+4)$.
And $x^2+4$ can be rewritten as $(x+2i)(x-2i)$