Exercise algebra.equations.quadratic.no-abc

Description
solve a quadratic equation without abc-formula

Derivation

10-x^2 == -x^2-5*x

⇒ algebra.equations.quadratic.cancel

10 == -5*x

⇒ algebra.equations.coverup.times

-2 == x

⇒ algebra.equations.linear.flip

x == -2