Question

Consider the polynomial function p given by p(x)=5x^3+6x^2+4x

evaluate the function at x=-5 and x=15

Answer 1

• p(-5) = -495
• p(15) = 18285

Explanation:

You want the value of p(x)=5x^3+6x^2+4x for x=-5 and x=15.

Horner form

Writing a polynomial in Horner form can simplify evaluation.

p(x) = ((5x +6)x +4)x

p(-5)

p(-5) = ((5(-5) +6)(-5) +4)(-5) = (-19(-5) +4)(-5) = 99(-5) = -495

p(15)

p(15) = ((5(15) +6)(15) +4)(15) = (81(15) +4)(15) = 1219(15) = 18285