Find the coefficient of $x^2$ in the expansion of the product $$(1-x)(1+2x)(1-3x)\dotsm(1+14x)(1-15x).$$
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<|im_start|>user
Find the coefficient of $x^2$ in the expansion of the product $$(1-x)(1+2x)(1-3x)\dotsm(1+14x)(1-15x).$$
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Find the coefficient of $x^2$ in the expansion of the product $$(1-x)(1+2x)(1-3x)\dotsm(1+14x)(1-15x).$$
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