One root of x^2 + 12x + k = 18x + 3 is twice the other root. Find k.
x2 + 12x + k = 18x + 3
x2 - 6x + (k-3) = 0
Let the roots be a, 2a
a + 2a = 6, a(2a) = k-3 => 3a = 6 => a = 2
2a2 = k - 3 => k - 3 = 8 => k = 11.
