“[T]he quintic equation.., equations of degree 5 or more, cannot be solved using only... roots... [T]hat took mathematicians 100s of years.., painfully. ...[E]verybody knows how to solve quadratic equations.., and with a lot more work... over a century or two, people worked out how to solve {{w|cubic equation}}s... [W]ith even... more hard work, finally they worked out how to solve equations of degree 4.., a famous landmark in mathematics, and then they got stuck. They couldn't do 5.”