Question

AJUTOOOOR !!!!! VA ROOOOG !!!!!! <3

Calculati : S=1²-2²+3²-4²+...+99²-100²

Answer 1

1^2-2^2=(1+2)(1-2) =-3
3^2-4^2=(3+4)(3-4)=-7
5^2-6^2=(5+6)(5-6)=-11 
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.99^2-100^2=(99+100)(99-100)=-199
Vom avea (-3)+(-7)+(-11)+......+(-199)  avem 50 termeni

(-3)+(-7)+(-11)+......+(-199)=(-3-199)x50/2=(-202)x25=-5050