Question

How do you combine like terms in (r−3)(r+1)+(r−3)(r+8)?

Answer 1

$(r - 3)(r + 1) + (r - 3)(r + 8) \\ = ({r}^{2} - 3r + r - 3) + ( {r}^{2} - 3r + 8r - 24) \\ = {r}^{2} - 2r - 3 + {r}^{2} + 5r - 24 \\ = 2 {r}^{2} + 3r - 27$