Question

Find the zeroes of a polynomial x cube -5x square- 16x+80, if its two zeroes are equal in magnitude but opposite in signs.

Answer 1

x^3-5x^2-16x+80
=x^2(x-5) -16(x-5)
=(x-5) (x^2-16)
=x^2-4^2
=(x-4)(x+4)
=x=4/-4/5
zeroes = 4 , -4 and 5