Question

What is the equation of a quadratic function p with rational coefficients that has a zero of 3-i

Answer 1

Answer:

p = x² − 6x + 10

Step-by-step explanation:

Complex roots come in conjugate pairs.  So if 3−i is a root, then 3+i is also a root.

p = (x − (3−i)) (x − (3+i))

p = x² − (3+i)x − (3−i)x + (3−i)(3+i)

p = x² − 3x − ix − 3x + ix + (9 − i²)

p = x² − 6x + 10

You can check your answer using the quadratic formula.

x = [ -b ± √(b² − 4ac) ] / 2a

x = [ 6 ± √(36 − 40) ] / 2

x = (6 ± 2i) / 2

x = 3 ± i