Exercise algebra.equations.quadratic.no-abc
Description
solve a quadratic equation without abc-formula
Derivation
![](http://ideas.cs.uu.nl/images/external.png)
x^2-6*x+9 == 3
⇒ algebra.equations.quadratic.left-square(x-3)^2 == 3
⇒ algebra.equations.coverup.powerx-3 == sqrt 3 or x-3 == -sqrt 3
⇒ algebra.equations.coverup.onevar.minus-leftx == 3+sqrt 3 or x-3 == -sqrt 3
⇒ algebra.equations.coverup.onevar.minus-leftx == 3+sqrt 3 or x == 3-sqrt 3