1²-2²+3²-4²+5²-6²+…+99²-100²
=(1+2)(1-2)+(3+4)(3-4)+...+(99+100)(99-100)
=-1-2-3-4-...-99-100
=-(1+2+...+100)
=-100×(1+100)÷2
=-5050;
1²-2²+3²-4²+5²-6²+…+99²-100²
=(1+2)(1-2)+(3+4)(3-4)+...+(99+100)(99-100)
=-1-2-3-4-...-99-100
=-(1+2+...+100)
=-100×(1+100)÷2
=-5050;