Exercise algebra.equations.quadratic.no-abc
Description
solve a quadratic equation without abc-formula
Derivation
![](http://ideas.cs.uu.nl/images/external.png)
x == 0 or 2*x-4 == 0
⇒ algebra.equations.coverup.onevar.minus-leftx == 0 or 2*x == 4
⇒ algebra.equations.coverup.timesx == 0 or x == 2