Question

Which expression represents the number 5i4+2i3+8i2+−4  rewritten in a+bi  form?

Answer 1

Thats not the answer. I need help with this answer too.

These are the answers we're supposed to choose from:

−3+2i

5+0i

5−2i

​−3−4i

−3+0i

Which one is it?

Answer 2

remember
i²=-1 so
i³=-i
i⁴=1

so
5i⁴+2i³+8i²-4
5(1)+2(-i)+8(-1)-4
5-2i-8-4
-7-2i is the form