Find the constant k such that the quadratic 2x^2 + 3x + 8x - x^2 + 4x + k has a double root.
Simplify as
x^2 + 15x + k
This will have a double root when the discriminant = 0
15^2 - 4 (1) k = 0
225 = 4k
k = 225 / 4
+713 
