Question

for what value of M is x³-2mx²+16 divisible by x+2?

Answer 1

$x + 2 = 0 \\ x = - 2 \\ x {}^{3} - 2mx {}^{2} + 16 = 0 \\ ( - 2) {}^{3} - 2 \times m \times ( - 2) {}^{2} + 16 = 0 \\ - 8 - 8m + 16 = 0 \\ 8 - 8m = 0 \\ 8m = - 8 \\ m = - 8 \div 8 \\ m = - 1$