Question #N315
If $x^2 + 3x - 10 = (x + 5)(x + k)$, what is the value of $k$?
A. -2
B. 2
C. -5
D. 5
Correct Answer is: A
We can solve for *k* by expanding the right side of the equation and then comparing coefficients. Expanding the right side, we get $(x+5)(x+k) = x^2 + (k+5)x + 5k$. For this to be equivalent to the left side, $x^2 + 3x - 10$, we need the coefficients of *x* to match. This means $k+5 = 3$, so $k = -2$.