Question

Write the simplest polynomial function with the given roots -5i, 2, and 7. I know 2 and 7 = (x - 2)(x - 7), but what do I do with -5i? How do I get rid of the i? Take the square root or..?

Answer 1

you have to use the conjugate of the imaginary number and make it (x-(-5i)(x-(5i)) and foil them and then you foil it all

Answer 2

Thanks! But how do I get rid of the I? I got: x^2 - 5i + 5i - 25i.

Answer 3

should be 25i^2 and with the two in the middle cant you cancel them out. remember I^2=-1

Answer 4

Ohh you are smart! Simple things like that are the ones that I forget. Thanks so much! So it would be x^2 + 25. Thanks so much! :-)

Answer 5

almost there lol. remember that I^2=-1 so you have 25-1

Answer 6

So would it be -25 or 24? I tried 24 and it didn't work I'm assuming it's -25??

Answer 7

Anyone else willing to help?

Answer 8

alright I looked at it again and if you foil the last term which are +5i and - 5i you get -25i^2 which is -26