E = \(\left(\frac{1}{57}-\frac{1}{5757}+\frac{1}{23}\right)\left(\frac{1}{2}-\frac{1}{3}-\frac{1}{6}\right)\)
E = \(\left(\frac{1}{57}-\frac{1}{5757}+\frac{1}{23}\right).0\)
E = 0
1.Tính E= (1/57 - 1/5757 + 1/23) . (1/2 - 1/3 - 1/6)
2.
a. Chứng tỏ rằng: 1/n + 1/n+1 = 1/n - 1/n+1
b. Tính nhanh: 1/1 + 1/2 + 1/2 . 1/3 + 1/3 . 1/4 + .......+ 1/998 . 1/999 + 1/999 . 1/1000
3. Tìm số tự nhiên x: 1/3 + 1/6 - 1/10 +.....1/x(x+1):2 = 2001/2003
Tính giá trị biểu thức một cách hợp lí
1) B = 5 − 3 4 + 1 5 − 6 + 7 4 − 8 5 − 2 − 5 4 + 16 5
2) C = − 2 3 + 1 − 7 5 − 0 , 2 + 7 15 − 1 + 4 3
3) D = − 0 , 25 − − 3 4 − − 7 3 + − 9 2 − 5 6
4) E = 1 − 2 5 − 4 3 − 0 , 8 − 1 − 1 , 4 + 2
Tính hợp lí:
A= -2/9 + -3/4 + 3/5 + 1/15 + 1/57 + 1/3 + -1/36
B= 1/2 + (-1/5 )+ (-5/7) + 1/6 + (-3/35) + 1/3 + 1/41
Tính nhanh :
\(C=\frac{1}{3}+\frac{-3}{4}+\frac{3}{5}+\frac{1}{57}+\frac{-1}{36}+\frac{1}{15}+\frac{-2}{9}\)
\(D=\frac{1}{2}+\frac{-1}{5}+\frac{-5}{7}+\frac{1}{6}+\frac{-3}{35}+\frac{1}{3}+\frac{1}{41}\)
\(E=\frac{-1}{2}+\frac{3}{5}+\frac{-1}{9}+\frac{1}{127}+\frac{-7}{18}+\frac{4}{35}+\frac{2}{7}\)
1. Tính hợp lí:
a) B = 1/2 - [ 3/8 + ( -7/4 ) ]
b) -4/12 - ( -13/39 - 0,25 ) + 0,75
c) 1/2 - 1/3 + 1/23 + 1/6
d) ( -13/7 - 4/9) - ( -10/7 - 4/9 )
e) ( 7/8 - 5/2 + 4/7 ) - ( -3/7 + 1 - 13/8 )
f) -3/7 + ( 3 - 3/4 ) - ( 2,25 - 10/7)
g) ( 5/3 - 3/7 + 9 ) - ( 2 + 5/7 - 2/3 ) + ( 8/7 - 4/3 - 10 )
thực hiện phép tính
\(l.\dfrac{\dfrac{1}{3}+\dfrac{1}{7}-\dfrac{1}{23}}{\dfrac{2}{3}+\dfrac{2}{7}-\dfrac{2}{23}}\times\dfrac{\dfrac{1}{3}-0.25-0.2}{1\dfrac{1}{6}-0.875-0.7}\)
5454/5757-171717/191919 .3/4+1/4:x=2/5
(13/2020+23/2021-33/2022)-(1/2-1/3-1/6) tính nhanh
