作业帮sn=(x-1)+(x^2-3)+(x^3-5)+...+[x^n-(2n-1)]
来源：学生作业帮助网 编辑：作业帮 时间：2024/05/04 06:08:04
![sn=(x-1)+(x^2-3)+(x^3-5)+...+[x^n-(2n-1)]](/uploads/image/z/6934723-43-3.jpg?t=sn%3D%28x-1%29%2B%28x%5E2-3%29%2B%28x%5E3-5%29%2B...%2B%5Bx%5En-%282n-1%29%5D)
sn=(x-1)+(x^2-3)+(x^3-5)+...+[x^n-(2n-1)]
sn=(x-1)+(x^2-3)+(x^3-5)+...+[x^n-(2n-1)]
sn=(x-1)+(x^2-3)+(x^3-5)+...+[x^n-(2n-1)]
sn=(x-1)+(x^2-3)+(x^3-5)+...+[x^n-(2n-1)]
=x+x^2+x^3+.+x^n+1+3+5+.+2n-1
=x(1-x^n)/(1-x)+(1+2n-1)*n/2
=x(1-x^n)/(1-x)+n^2