Exercise algebra.equations.quadratic.no-abc

Description
solve a quadratic equation without abc-formula

Derivation

-(x+2)*(x+6)+2*x^2-6*x-3 == 0

⇒ algebra.equations.linear.distr-times

-x^2-8*x-12+2*x^2-6*x-3 == 0

⇒ algebra.equations.linear.merge

x^2-14*x-15 == 0

⇒ algebra.equations.quadratic.nice-factors

(x+1)*(x-15) == 0

⇒ algebra.equations.quadratic.product-zero

x == -1 or x == 15