Question

Tính x  biết  1+2+3+.....99+100 =100 -  x 

Answer 1

1 + 2 + 3 + ..... + 100 = 100 - x

100.(100 + 1):2 = 100 - x

5050 = 100 - x

x = 100 - 5050

x=  -4950