1+2²+2^3+2^4……+2^99-2^100=1+2²+2^3+2^4……+2^99(1-2)=1+2²+2^3+2^4……-2^99=1+2²+2^3+2^4……-2^98=1+2²+2^3+2^4……+2^97=---------------=1+2²-2³=5-8=-3