Question

If sum of the square of zeroes of the quadratic polynomial f (x) = x^2-4x+k is 20 find k

Answer 1

let the zeroes are a and b

a2 + b2 = 20
(a+b)2 - 2ab = 20
4^2 - 2k = 20
16 - 2k = 20
-2k = 20 -16 = 4
k = 4/(-2)
k = -2