Exercise algebra.equations.quadratic.no-abc
Description
solve a quadratic equation without abc-formula
Derivation
![](http://ideas.cs.uu.nl/images/external.png)
x^2-14*x-15 == 0
⇒ algebra.equations.quadratic.nice-factors(x+1)*(x-15) == 0
⇒ algebra.equations.quadratic.product-zerox == -1 or x == 15