Question

if the sum of squares of zeroes of quadratic polynomial f[x]=x*x-8x+k is 40,find the value of k

Answer 1

let a,b be roots then a*a + b*b = (a+b)*(a+b) - 2a*b
since a+b is 8 and ab is k
-> 8*8 -2*k = 40
-> 64 -2k = 40
-> k = 12