What causes the need for imaginary numbers

Well one example of why we need them is because we want polynomials to always the factor. In the real numbers, the polynomial x2+1 doesn't factor. There are no real roots of this polynomial. But the complex numbers are special in that no matter what polynomial you have, it will always factor in the complex numbers.

Good luck! :)

Sometimes, in higher levels of math you will get something like, the square root of negative four, except that isn't possible, but you still need it to find the answer.  Thats why you use imaginary numbers.  the square root of negative four is 2i

All you have to do is multiply