Tính:  1+ ( 1+ 2)+ ( 1+ 2+ 3) +.....+ ( 1+ 2+....+98)/ 1. 98+ 2. 97+ 3. 96+....+ 98. 1

1+(1+2)+(1+2+3)+...+(1+2+3+...+98)

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1*98+2*97+3*96+....+98*1

cho B=1*98+2*97+3*6+..+2*97+1*98/1*2+2*3+3*4+97*98+98*99

1*98+2*97+....+98*1

1*2+2*3+...+98*99

Tính \(T=\left(\frac{2}{98}+\frac{3}{97}+...+\frac{99}{1}\right)X\left(\frac{1}{99}+\frac{2}{98}+...+\frac{98}{2}\right)-\left(\frac{1}{99}+\frac{2}{98}+..+\frac{99}{1}\right)X\left(\frac{2}{98}+\frac{3}{97}+...+\frac{98}{2}\right)\)

1 + [1+2] +[172+3]+...+[1+2+3+...+98] chia 1 nhan 98 +2  nhan 97 +3  nhan 96 +...+98 nhan 1

Tính nhanh

a.(1+1/2)×(1+1/3)×(1+1/4)×...×(1+1/98)×(1+1/99).

b.1/2×2/3×3/4×...×97/98×98/99×99/100

D=(1*98+2*97+3*96+..+98*1)/(1*2+2*3+3*4+...98*99)

Giúp mình nhé!

A=1/2+1/3+1/4+....+1/100

B=99/1+98/2+97/3+....+2/98+1/99

-1 / 100 . 99 - 1 / 99 . 98 - 1 / 98 . 97 - ... -1 / 3 . 2 - 1 / 2 . 1