Exercise algebra.equations.quadratic.no-abc

Description
solve a quadratic equation without abc-formula

Derivation

x^2 == 15-8*x

⇒ algebra.equations.quadratic.move-left

x^2+8*x-15 == 0

⇒ algebra.equations.quadratic.prepare-split

x^2+8*x+16 == 31

⇒ algebra.equations.quadratic.left-square

(x+4)^2 == 31

⇒ algebra.equations.coverup.power

x+4 == sqrt 31 or x+4 == -sqrt 31

⇒ algebra.equations.coverup.onevar.plus

x == -4+sqrt 31 or x+4 == -sqrt 31

⇒ algebra.equations.coverup.onevar.plus

x == -4+sqrt 31 or x == -4-sqrt 31