May 10: Finding Complex Roots of a Polynomial

Post date: May 10, 2013 9:14:05 PM

Notes:

Given the real root of x^3-1x^2-7x+15 is -3, what are the imaginary roots?

1) use synthetic division to find the trinomial

-3I 1 -1 -7 15

-3 12 -15 x^2-4x+5

1 -4 5 0

2) Use the Quadratic formula to solve for the other two roots

4+/-sqrt(-4^2-4(5)(1)) = 4+/-sqrt(16-20) = 4+/-sqrt(-4) = 4+/-2i = 2+i or 2-i

2(1) 2 2 2

Homework:

Continue working on Polynomial Review Packet

TEST ON THURSDAY 5/16