Question

当x=-1时,求x+2x²+3x³+……+99x^99+100x^100的值

Answer 1

x+2x²+3x³+……+99x^99+100x^100

=-1+2-3+4-5+6+.+(-99)+100

=(-1+2)+(-3+4)+(-5+6)+.+(-99+100)

=1+1+1+...+1

=1*50

=50