# Math Help - [SOLVED] Quadratic equation

$(x^2-4x)^2 -26(x^2-4x)+105=0$
It *should* be solved using new variable, but I can't figure it out for x^3.

2. Hello,
Originally Posted by courteous
$(x^2-4x)^2 -26(x^2-4x)+105=0$
$({\color{red}x^2-4x})^2 -26({\color{red}x^2-4x})+105=0$
So if you substitute $y={\color{red}x^2-4x}$, you'll have ... ?