B=8/9+8/10+8/11+...+8/100 phần 1/45+1/50+1/55+...+1/500
Tính hợp lý
\(A= (\dfrac{92-\dfrac{1}{9}-\dfrac{2}{10}-\dfrac{3}{11}-...-\dfrac{91}{99}-\dfrac{92}{100}}{\dfrac{1}{45}+\dfrac{1}{50}+\dfrac{1}{55}+...+\dfrac{1}{495}+\dfrac{1}{500}}\) B= \(\dfrac{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{8}+\dfrac{1}{9}+\dfrac{1}{10}}{\dfrac{1}{9}+\dfrac{2}{8}+\dfrac{3}{7}+...+\dfrac{8}{2}+\dfrac{9}{1}})\)
Tính hợp lí:
A= \(\dfrac{92-\dfrac{1}{9}-\dfrac{2}{10}-\dfrac{3}{11}-...-\dfrac{91}{99}-\dfrac{92}{100}}{\dfrac{1}{45}+\dfrac{1}{50}+\dfrac{1}{55}+...+\dfrac{1}{495}+\dfrac{1}{500}}\)
B= \(\dfrac{\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{8}+\dfrac{1}{9}+\dfrac{1}{10}}{\dfrac{1}{9}+\dfrac{2}{8}+\dfrac{3}{7}+...+\dfrac{8}{2}+\dfrac{9}{1}}\)
Cái này mk từng làm nhưng có chút sai sót vậy nên bn sữa cho mk chút nhé ! Thay vì N = ... thì bn thay bằng A = ... nha
Ta có :
N = 40 ( A = 40 )
(92-1/9-2/10-3/11-...-92/100)/(1/45+1/50+1/55+...+1/500)
[92-1/9-2/10-3/11-....-92/100]:[1/45+1/50+1/55+....1/500]
Tính:(92-1/9-2/10-3/11-.......-92/100):(1/45+1/50+1/55+...+1/500)
tính [92-1/9-2/10-3/11-...-92/100]:[1/45+/50+1/55+...+1/500]
a) So sánh: -22/45 và -51/103
b) Tính:
( 92 - 1/9 - 2/10 - 3/11 - ... - 92/100 ) : ( 1/45 + 1/50 + 1/55 + ... + 1/500 )
92-1/9-2/10-3/11-....-92/100
------------------------------------
1/45+1/50+1/55+......+1/500
Tính B= M/N với
M= 92- 1/9 - 2/10 - 3/11 - ...........90/98 - 91/99 - 92/100
N= 1/45 + 1/50 + 1/55 + ............1/145 + 1/500
Giải:
M=9/9+10/10+11/11+....+ 100/100 - 1/9 - 2/9 - 3/9 -.....90/98 - 91/99 - 92/100
= ( 9/9 - 1/9) + (10/10 - 2/10) + .......+ (100/100 - 92/100) = 8/9 + 8/10+ 8/11+....+ 8/100 = 8 ( 1/9+1/10 +...+ 1/100). Đặt 8 ra ngoài
N=1/5( 1/9+1/10+...+ 1/100). Đặt 1/5 ra ngoài
Suy ra :
B=M/N=8/1/5=40
chuan chua
(92- 1/9 - 2/10 - 3/11 - .....- 92/100) : ( 1/45 + 1/50 + 1/55 + .....+ 1/ 500 )
= (1-1/9 + 1- 2/10 + 1- 3/11...+1 - 92/100) : 1/5 x (1/9 +1/10 + 1/11+...+1/100)
= ( 8/9 + 8/10 + 8/11 + 8/11...+ 8/100) : 1/5 x (1/9 +1/10 + 1/11+...+1/100)
= 8 x (1/9 +1/10 + 1/11+...+1/100) : 1/5 x (1/9 +1/10 + 1/11+...+1/100)
= 8 : 1/5
= 40
[92--1/9-2/10-3/11-4/12-92/100] :[1/45+1/50+1/55+1/60+1/500]