Question

Omg! hopefully I can post properly this time !!!!
Can someone please help me with this quadratic equation ?

Answer 1

A quadratic equation with real number coefficients and has 3 + 4i as one of it's roots, what's the other rooot?

Answer 2

3-4i

Answer 3

must be 3-4i
I think...

Answer 4

how do you know though? :(

Answer 5

\[x=(-b \pm \sqrt{b^2-4ac})/2a\]
it's the part under the radical that makes the "+4i" part, so since the two roots differ by the "plus or minus" the other root should be the "-4i"

Answer 6

complex roots always exist in conjugate pairs, so if a+bi is a root then the other root will definitely be a-bi