How do you solve #x (x^2 + 2x + 3)=4#?
It would be great if we could now factor the left-hand side. Unfortunately, the roots of this are an irrational real number as well as two complex numbers with irrational real and imaginary parts.
Using a computer or calculator gives approximate roots:
There is a method/formula for finding exact expressions for these roots (involving roots that are irrational), but it's not pleasant:
general method/formula for cubic roots on Wikipedia