What is the remainder when x^3 + 2x − 5 is divided by (x + 1)?

解說

By the remainder theorem the remainder is f(−1) = −1 − 2 − 5 = −8. The value −2 is f(1), from using the wrong substitution. A remainder of 0 would mean that (x + 1) is a factor, which it is not.