The polynomial x³ + x² - 10x + 8 has x = 1 as one of its roots. What is the sum of the other two roots?

Since $x = 1$ is a root, $x - 1$ is a factor. Dividing gives $x^3 + x^2 - 10x + 8 = (x - 1)(x^2 + 2x - 8)$. The other roots solve $x^2 + 2x - 8 = 0$, which factors as $(x + 4)(x - 2) = 0$, so they are $-4$ and $2$. Their sum is $-2$, choice C, which matches Vieta's formula: the negative of the $x$-coefficient, $-2$. Choice A (2) is one of the roots and also the sum with the wrong sign. Choice B (8) is the constant term of the cubic. Choice D (1) is the known root, not the sum of the other two.