1/99 -1/99*98 - 1/98*97 -...-1/2-1
Tính \(T=\left(\frac{2}{98}+\frac{3}{97}+...+\frac{99}{1}\right)X\left(\frac{1}{99}+\frac{2}{98}+...+\frac{98}{2}\right)-\left(\frac{1}{99}+\frac{2}{98}+..+\frac{99}{1}\right)X\left(\frac{2}{98}+\frac{3}{97}+...+\frac{98}{2}\right)\)
Giải giúp mình nhé:
1. ( 91-99+98)-(-99+98)
2. ( 99-98+97)-(99+97+98)
(91-99+98)-(-99+98)=91-99+98+99-98=91
(99-98+97)-(99+97+98)=99-98+97-99-97-98=(-98)*2=-196
1. (91 - 99 + 98) - (-99 + 98)
= 91 - 99 + 98 + 99 - 98
= (-99 + 99) + (98 - 98) + 91
= 0 + 0 + 91
= 91
2. (99 - 98 + 97) - (99 + 97 + 98)
= 99 - 98 + 97 - 99 - 97 - 98
= (99 - 99) + (97 - 97) + (-98 - 98)
= 0 + 0 + (-196)
= -196
1\99*100-1\99*98-1\97*98-................-1\2*1
-1 / 100 . 99 - 1 / 99 . 98 - 1 / 98 . 97 - ... -1 / 3 . 2 - 1 / 2 . 1
Vậy bạn làm như thế nào? Chỉ mình đi
Tính:1:99/100:98/99:97/98:....:2/3:1/2
Tính nhanh
1/100 - 1/ 100 . 99 - 1/99 . 98 - 1/ 97 .98 - 1/ 97 .98 - ..- 1/ 3.2 - 1/2.1
đề :
= 1/100 - (1 / 100.99 +1/99.98 + ...+ 1/3.2 +1/2.1 )
=1/100 - (1 /1.2 +1/ 2.3 +...+ 1/ 98.99 +1 / 99.100)
=1/100 -( 1- 1/ 2 +1/2 -1/3 +...+1/98 -1/99 +1/99 -1/100)
=1/100 - ( 1- 1/100)
=1/100 - 99 /100
= -98/100
= -49 /50
99/1+98/2+97/3+................+2/98+1/99
1/2+1/3+1/4+.......................+1/99+1/100
A=1/2+1/3+1/4+....+1/100
B=99/1+98/2+97/3+....+2/98+1/99
tinh 1*99+2*98+3*97+....+98*2+99*1