\(\dfrac{1}{2\cdot5}+\dfrac{1}{3\cdot5}+\dfrac{1}{3\cdot7}+\dfrac{1}{4\cdot7}+...+\dfrac{1}{9\cdot19}+\dfrac{1}{10\cdot19}=\dfrac{3+2}{2.3.5}+\dfrac{4+3}{3\cdot4\cdot7}+...+\dfrac{10+9}{9\cdot10\cdot19}=\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{9.10}=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{9}-\dfrac{1}{10}=\dfrac{1}{2}-\dfrac{1}{10}=\dfrac{2}{5}\)
1. Tính :
a. 3/5- -7/10-13/20
b. 3/4+ -1/3-5/18
c. 3/14-5/-8+ -1/2
d. 1/2+ 1/-3+1/4- -1/6
đ. 19/24-1/2-1/3- 7/24
g. -1/3+1/2-5/6
e. 4/-9+8/5+ -5/9-2/11+7/15
ê. 7/11-(3/5+7/11)
Nhờ các bạn giúp mình vs cảm ơn các bạn nhiều. Mình tick cho.
a. 19+(29-9*37)-(63*9-29*99)
b.1/2+1/4+1/8+1/16+1/32+1/64+1/128
c. 5*4^15*9^9-4*3^20*8^9
____________________________
5*2^9*6^19-7*2^29*27^6
ý c la phan số nhé
Bài 1: Thực hiện phép tính bằng cách hợp lí < nếu có thể >
a, \(\left(-1,5\right).\left(1+\frac{2}{3}\right)+1,4.\frac{15}{49}-\left(\frac{4}{5}+\frac{2}{3}\right):2\frac{1}{5}\)
b, \(\frac{7}{5}+\frac{4}{5}\left(\frac{5}{8}-\frac{7}{4}\right)+2014^0\)
c, \(1\frac{3}{25}+\frac{17}{19}-\frac{3}{25}+0,9+\frac{2}{19}\)
d, \(-\frac{5}{9}.\frac{6}{13}+\frac{-5}{9}.\frac{7}{23}+\frac{5}{23}:\frac{9}{7}\)
Bài 2: Tìm x, biết
a, 20%x + 0,4x = 4,5
b, \(\left(3\frac{1}{2}-2\left|x-1\right|\right).2\frac{2}{3}=5\frac{1}{3}\)
HELP MEEEEE
Bài 1: Thực hiện phép tính bằng cách hợp lí ( nếu có thể )
a, \(\left(-1,5\right).\left(1+\frac{2}{3}\right)+1,4.\frac{15}{49}-\left(\frac{4}{5}+\frac{2}{3}\right):2\frac{1}{5}\)
b, \(\frac{7}{5}+\frac{4}{5}\left(\frac{5}{8}-\frac{7}{4}\right)+2014^0\)
c, \(1\frac{3}{25}+\frac{17}{19}-\frac{3}{25}+0,9+\frac{2}{19}\)
d, \(-\frac{5}{9}.\frac{6}{13}+\frac{-5}{9}.\frac{7}{23}+\frac{5}{23}:\frac{9}{7}\)
Bài 2: Tìm x, biết:
a, 20%x + 0,4x = 4,5
b, \(\left(3\frac{1}{2}-2\left|x-1\right|\right).2\frac{2}{3}=5\frac{1}{3}\)
HELP ME!
Bài 2: Thực hiện phép tính một cách hợp lí
f) \(\dfrac{7}{19}\) . \(\dfrac{8}{11}\) + \(\dfrac{3}{11}\) . \(\dfrac{7}{19}\) +\(\dfrac{-12}{19}\)
i) ( \(\dfrac{3}{8}\) + \(\dfrac{-3}{4}\)+ \(\dfrac{7}{12}\) ) : \(\dfrac{5}{6}\) +\(\dfrac{1}{2}\)
1. Tính nhanh
a) A=1/ 5 .6 + 1/ 6 .7 + 1/ 7. 8+ ... + 1/24 . 25
b) B= 2/ 3 .5 + 11/ 8 .19 + 13/ 19 .32 + 25/ 32 . 57 + 30/ 57 . 87
Thực hiện phép tính ( tính nhanh nếu có thể )
a, -5/21 + -2/21 + 8/24
b, 4/11 . -2/7 + 4/11 . -4/7 + 4/11 . -1/7
c, \(10\dfrac{5}{9}\) - ( \(3\dfrac{5}{7}\) + \(4\dfrac{5}{9}\) )
d, 1/3 + \(1\dfrac{3}{4}\) - ( \(1\dfrac{3}{4}\) - 80% )
e, \(5\dfrac{3}{5}\) + \(7\dfrac{21}{48}\) : 10/7 - \(5\dfrac{21}{48}\) : 10/7
f, -5/7 . 2/11 - 5/11 . 9/7 + \(2\dfrac{5}{7}\)
g, -3/13 . 6/8 + 7/13 . -3/8 + \(1\dfrac{3}{8}\)
Câu trả lời:
a)2/3+1/5.10/7
b)17/18-11/6
c)7/12-27/7.1/18
d)3/10.(-5/6)-1/8
e)(-4/9).3/8+1/8
f)2/7+28/27:(-4/9)
g)(1/2-2/3).4/5
h)9/7.(3/7-1/2)
j) \(\dfrac{-3}{4}\) + \(\dfrac{2}{7}\) + \(\dfrac{-1}{4}\) +\(\dfrac{3}{5}\) +\(\dfrac{5}{7}\)
k) \(\dfrac{-2}{17}\)+ \(\dfrac{15}{23}\) + \(\dfrac{-15}{17}\) + \(\dfrac{4}{19}\) +\(\dfrac{8}{23}\)
