Complex zero question! check my answer please?

Question

anonymous · Answer

@ryanvarghese12790 it has to be either C or D..do you know the answer?

anonymous · Answer

@amistre64 another question similar to the other. I cant tell if its C or D.

amistre64 · Answer

rule of sign, how many possible negative roots do we have?

amistre64 · Answer

no negative roots, so that leaves us with x=9 as the only reasonable answer.

divide out the x=9 and see whats left over.

anonymous · Answer

attachment

amistre64 · Answer

1 -9   9  -81
    0   9   0    81
9  1   0   9     0

x^2 + 9 = 0 gives the complex parts

anonymous · Answer

yes so we know 9 is a root. i knew that. i just dont know how to find the other number.

amistre64 · Answer

ok, D is good,   sqrt(-9)  is 3i

anonymous · Answer

how do you find the 3i?

amistre64 · Answer

i worked a synthetic division method to determine what we had left over when we divide out x-9

amistre64 · Answer

x^2 + 9 = 0  is whats left,  solve for x

anonymous · Answer

ohh okay, thank you!

amistre64 · Answer

yw