1-2^2+3^2-4^2+5^2-6^2+```+99^2-100^2
=(1+2)(1-2)+(3+4)(3-4)+(5+6)(5-6)+……+(99+100)(99-100)
=-1-2-3-4-5-6-……-99-100
=-1×(1+2+3+4+5+6+……+99+100)
=-1×(1+100)×50
=-5050
1-2^2+3^2-4^2+5^2-6^2+```+99^2-100^2
=(1-2)(1+2)+(3-4)(3+4)+.....+(99-100)(99+100)
=-1-2-3-4-.....-99-100
=-5050
-220