Question 390472
A fast way to solve this problem is to know that the sum of the roots of a quadratic is {{{-b/a}}}, or -9 in this case. Since one of the roots is -2, the other one must be (-9) - (-2), or -7. Amazing that we don't even need to solve for k to find the other root?


(In general, the sum of the roots of any polynomial {{{ax^n + bx^(n-1) + ...}}} is -b/a. This is one of Vieta's formulas.