Crossword puzzle clue "x in an equation"

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

Like the equation ax^3 + bx^2 + cx + d = 0

Magnetic equation formulated by physicist Marie

Sort of gear — sort of equation