Question

1-2+3-4+5-...99+100 =

Answer 1

Deci ex arata astfel : 1-2+3-4+5-...99-100
 =(1+3+5+7+.....99) - (2+4+6+....+100)
=$\frac{50}{2}$[(2*1)+(50-1)*2] - $\frac{50}{2}$[(2*2)+(50-1)*2] 
=25[(2+98) - (4+98)]
=25[100-102]
=25* (-2)
= - 50
Pai cam asa se rezzolva