1+1+1+1+1+1+5+745+4+5+7+5+75+75+7+5645+8547851+5486878+46886654=?
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\(1)\frac{1}{3}.\frac{4}{5}+\frac{1}{3}.\frac{6}{5}-\frac{1}{3}\)
\(=\frac{1}{3}\left(\frac{4}{5}+\frac{6}{5}\right)\)
\(=\frac{1}{3}.2\)
\(=\frac{2}{3}\)
\(1)\)\(\frac{1}{3}.\frac{4}{5}+\frac{1}{3}.\frac{6}{5}-\frac{1}{3}\)
\(=\frac{1}{3}.\left(\frac{4}{5}+\frac{6}{5}-1\right)\)
\(=\frac{1}{3}.\left(\frac{4}{5}+\frac{6}{5}-\frac{5}{5}\right)\)
\(=\frac{1}{3}.1\)
\(=\frac{1}{3}\)
\(2)\)\(\frac{3}{7}.\frac{9}{26}-\frac{1}{14}.\frac{1}{13}\)
\(=\frac{1}{7}.\frac{27}{26}-\frac{1}{7}.\frac{1}{26}\)
\(=\left(\frac{27}{26}-\frac{1}{26}\right).\frac{1}{7}\)
\(=1.\frac{1}{7}\)
\(=\frac{1}{7}\)
\(3)\)\(15\left(\frac{1}{5}-\frac{7}{15}+\frac{17}{3}\right)\)
\(=3-7+85\)
\(=81\)
\(4)\)\(38\left(2\frac{1}{19}-5\frac{7}{38}\right)\)
\(=38\left(\frac{39}{19}-\frac{197}{38}\right)\)
\(=78-197\)
\(=-119\)
\(5)\)\(75\left(\frac{-4}{25}+7\frac{1}{15}-5\frac{7}{75}\right)\)
\(=75\left(\frac{-4}{25}+\frac{106}{15}-\frac{382}{75}\right)\)
\(=-12+530-382\)
\(=136\)
Ddaeng
a) -7/25 . 11/13 + -7/25 . 2/13 - 18/25=-1
b) 5/7 . 1/3 - 5/7 . 1/4 - 5/7 . 1/12=0
c) 5 + 2/5 . 4+ 2/7 + 5 + 5/7 . 5+ 2/5=18
d) 75% - 3/2 + 0,5 - [ -1/2]^2=-1/2
\(=75.\left(34+66\right)-65.100\)
\(=75.100-65.100\)
\(=100.\left(75-65\right)\)
\(=100.10\)
\(=1000\)
\(\dfrac{4}{7}-\dfrac{1}{3}< \dfrac{1}{2}-\dfrac{2}{9}\)
\(\dfrac{125}{100}-\dfrac{48}{64}< \dfrac{6}{7}-\dfrac{14}{28}\)
\(\dfrac{7}{5}-\dfrac{22}{25}=\dfrac{1}{5}+\dfrac{4}{10}\)\(\dfrac{45}{75}+\dfrac{22}{33}>\dfrac{4}{5}+\dfrac{4}{6}\)
\(\dfrac{1}{3\cdot5}+\dfrac{1}{5\cdot7}+\dfrac{1}{7\cdot9}+...+\dfrac{1}{x\left(x+2\right)}=\dfrac{11}{75}\left(x\ne0;x\ne-2\right)\)
\(\dfrac{2}{3\cdot5}+\dfrac{2}{5\cdot7}+\dfrac{2}{7\cdot9}+...+\dfrac{2}{x\left(x+2\right)}=\dfrac{22}{75}\)
\(\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{x}-\dfrac{1}{x+2}=\dfrac{22}{75}\)
\(\dfrac{1}{3}-\dfrac{1}{x+2}=\dfrac{22}{75}\)
\(\dfrac{1}{x+2}=\dfrac{1}{3}-\dfrac{22}{75}\)
\(\dfrac{1}{x+2}=\dfrac{1}{25}\)
suy ra
\(x+2=25\\ x=23\left(tm\right)\)
=>2/3*5+2/5*7+...+2/x(x+2)=22/75
=>1/3-1/5+1/5-1/7+...+1/x-1/x+2=22/75
=>1/3-1/x+2=22/75
=>1/x+2=25/75-22/75=3/75=1/25
=>x=23
a: =(5/7+2/7)+(4/3+5/3)=3+1=4
b: =(17/12+7/12)+(29/7-8/7)
=2+3=5
c: =(2/5+3/5)+(6/9+1/3)+(7/4+1/4)
=1+2+1
=4
d: =(1/3+2/3)+(13/17+4/17)+(29/11+4/11)
=1+1+3=5
c) Ta có: \(\dfrac{3}{5}+\dfrac{-5}{20}+\dfrac{30}{75}+\dfrac{-7}{4}\)
\(=\dfrac{3}{5}+\dfrac{2}{5}+\dfrac{-1}{4}+\dfrac{-7}{4}\)
\(=1-2=-1\)
Giải:
a)-1/12+4/3=-1/12+16/12=15/12=5/4
b)(-4/14-3/15)-(1/5-20/35-(-1)).7
=-17/35-22/35.7
=-17/35-22/5
=-171/35
c)3/5+-5/20+30/75+-7/4
=3/5+-1/4+2/5+-7/4
=(3/5+2/5)+(-1/4+-7/4)
=1+-2
=-1
d)5/6.-12/14+7/13
=-5/7+7/13
=-16/91
e)2/-9-5/-36-1/4
=-1/12-1/4
=-1/3
f)2/23+-5/12+7/18+21/23+-7/12
=(2/23+21/23)+(-5/12+-7/12)+7/18
=1+-1+7/18
=7/18