(x-1)-(x-1)^2+(x-1)^3-(x-1)^4+(x-1)^5展開式中,求x^2的係數

(x-1)-(x-1)^2+(x-1)^3-(x-1)^4+(x-1)^5展開式中,求x^2的係數

-1+C32(-1)-C42+C52(-1)³;
=-1-3-6-10
=-20