Question

Given that the quadratic polynomial f(x)=3x^2+ax+b has real coefficients and f(x)=0 has a complex root 8+5i, what is the value of a+b?

Answer 1

The other root must be 8-5i, so
f(x) = 3(x-(8+5i))(x-(8-5i))
= 3((x-8)^2 + 5^2)
= 3(x^2-16x+89)
= 3x^2 - 48x + 267

a+b = 239

Answer 2

219 sir