SOLUTION: say u+iv (where u and v are real numbers, and i is the imaginary unit) is a root of a quadratic polynomial; then, is u-iv also a root of that polynomial? Why, or why not?

Algebra ->  Complex Numbers Imaginary Numbers Solvers and Lesson -> SOLUTION: say u+iv (where u and v are real numbers, and i is the imaginary unit) is a root of a quadratic polynomial; then, is u-iv also a root of that polynomial? Why, or why not?       Log On


   



Question 384096: say u+iv (where u and v are real numbers, and i is the imaginary unit) is a root of a quadratic polynomial; then, is u-iv also a root of that polynomial? Why, or why not?
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
Yes. From the quadratic formula, we have
x+=+%28-b+%2B-+sqrt%28b%5E2+-+4ac%29%29%2F2a
Suppose the discriminant was negative. Then, this value x becomes
%28-b+%2B-+di%29%2F2a+=+%28-b%2F2a%29+%2B-+%28d%2F2a%29i where d is real. We can assign arbitrary values u and v to obtain
x = u+%2B-+vi.