# Coefficient of $$x^2$$

Let $$\color{orange}{C}$$ be the coefficient of $$\color{green}{x^2}$$ in $$\color{purple}{(1-x)(1+2x)(1-3x)(1+4x).........(1+14x)(1-15x)}$$. Find $$\color{orange}{|C|}$$.

[Credits to my math teacher.]

×