(1-2²)+(3²-4²)+(5²-6²)+······+(99²-100²)=∑((2n-1)²-(2n)²),n=1,2,3,4,.,50=∑(1-4n),n=1,2,3,4,.,50=((1-4*1)+(1-4*50))*50/2=(-3-199)*50/2=-202*50/2=-50...