Crossword puzzle clue "equation answer"

Equation answer

Find the answer to, as an equation

Answer, when pointing to this answer, to the question "Which letters answer this clue?"

Mathematician who proved the impossibility of solving the quintic equation

Equation math

Type of math equation

Creature whose probable existence in the universe is explored by the Drake equation

Girolamo ___, Italian mathematician who first published the solution to the general cubic equation