tính: A=1.98+2.97+3.96+…+98.1/1.2+2.3+3.4+…+98.99

0 bình luận về “tính: A=1.98+2.97+3.96+…+98.1/1.2+2.3+3.4+…+98.99”

1. Đặt `B=1*2+2*3+3*4+…+98*99=(98*99*100)/3`

   `A=[2(100-1)+3(100-2)+…+98(100-99)]/B`

   `A=[100(1+2+3+…+98)-B]/B`

   `A=[100(1+…+98)]/B-1`

   `A=(100*99*98/2)/B-1`

   `A=[100*99*98/2]/[99*98*100/3]-1`

   `A=(1/2)/(1/3)-1`

   `A=1/2`

   Trả lời