Solve for the unknown coefficient in this quadratic equation.
Level
1
If the roots of a quadratic equation x x + k x + 18 =0 are in the ratio of 1 is to 2 what could be a possible value of "k".
18
3
9
1
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1 solution
Given equation is x x + k x + 18 = 0 Let the two roots be r1 and r2. So r2 = 2r1.
Sum of two roots = - k which implies that 3r1 = -k .....(1) Product of two roots in the given equation = 18 which implies that 2 r1 r1 = 18 (2).
From (2) we solve r1 as +/- 3 , so k = - 3 * r1 , so k = +/- 9