1-2²+3²-4²+5²-6²+……+99²-100²+101²
=(1²-2²)+(3²-4²)+(5²-6²)+……+(99²-100²)+101²
=(1-2)(1+2)+(3-4)(3+4) +(5-6)(5+6)+……+(99-100)(99+100)+101²
=-(1+2)-(3+4)_(5+6)-……-(99+100)+101²
=-(1+2+3+4+5+……+99+100)+101²
=-5050+101²
=5151
1-2²+3²-4²+5²-6²+……+99²-100²+101²
=(1²-2²)+(3²-4²)+(5²-6²)+……+(99²-100²)+101²
=(1-2)(1+2)+(3-4)(3+4) +(5-6)(5+6)+……+(99-100)(99+100)+101²
=-(1+2)-(3+4)_(5+6)-……-(99+100)+101²
=-(1+2+3+4+5+……+99+100)+101²
=-5050+101²
=5151