Quartic equations are simply defined as polynomials that have a degree of four.
Therefore, it will have four roots. These 4 roots are complex roots because they may have real and imaginary solutions. I said it may have real and imaginary roots because it's not every quartic equation that will have four real roots because for example, it could have real roots of maybe 0, 1, 2, 3, 4 and also imaginary roots to make it four roots in total.
