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`#lv`
`-2/5+(-7/10)-9/6`
`=-2/5-7/10-9/6`
`=-4/10-7/10-9/6`
`=-11/10-3/2`
`=-11/10-15/10`
`=-26/10`
`=-13/5`
__
`1/2+(-2/5)-(-2/3)`
`=1/2-2/5+2/3`
`=5/10-4/10+2/3`
`=1/10+2/3`
`=3/30+20/30`
`=23/30`
__
`5/3-3/4+7/6`
`=20/12-9/12+14/12`
`=11/12+14/12`
`=25/12`
__
`-1/5+5/3-3/2`
`=-3/15+25/15-3/2`
`=22/15-3/2`
`=44/30-45/30`
`=-1/30`
__
`1/4-7/8+(-9/10)`
`=2/8-7/8-9/10`
`=-5/8-9/10`
`=-25/40-36/40`
`=-61/40`
__
`5/4+1/2+(-7/12)`
`=15/12+6/12-7/12`
`=21/12-7/12`
`=14/12`
`=7/6`
__
`-5/8-1/3+(-7/6)`
`=-5/8-1/3-7/6`
`=-15/24-8/24-28/24`
`=-52/24`
`=-13/6`
__
`-3/4-7/10+(-5/6)`
`=-3/4-7/10-5/6`
`=-45/60-42/60-50/60`
`=-137/60`
Bài làm
a, (-2/5) + (-7/10) - 9/6 =(-12/30) + (-21/30) - 45/30=(-33/30) - 45/30 = (-78/30)
b,1/2 + (-2/5) - (-2/3) = 15/30 + (-12/30) - (-20/30) = 3/30 - (-20/30) = 23/30
c,5/3 - 3/4 + 7/6 = 40/24 - 18/24 + 28/24 = 22/24 + 28/24 = 50/24 = 25/12
d, (-1/5) + 5/3 - 3/2 = (-6/30) + 50/30 - 45/30 = 44/30 - 45/30 = (-1/30)
e, 1/4 - 7/8 + (-9/10) = 10/40 - 35/40 - 36/40 = (-25/40) - 36/40 = (-61/40)
f, 5/4 +1/2 + (-7/12) = 15/12 + 6/12 - 7/12 = 21/12 - 7/12 = 14/12 = 7/6
g,(-5/8) -1/3 + (-7/6) = (-15/24) - 8/24 - 28/24 = (-23/24) - 28/24 = (-51/24)
k,(-3/4) - 7/10 + (-5/6) = (-45/60) - 42/60 - 50/60 = (-87/60) - 50/60 = (-137/60)
chúc bn học tốt nha
sai thì mn góp ý giúp mk
#\(N\)
`1, -3/7 +5/13 - 4/7 +-8/13 = (-3/7 + -4/7) + (5/13 --8/13) = -1+1=0`
`2, -5/14 - 2/14 + 1/8 + 1/8 = (-5/14 - 2/14) + (1/8 + 1/8) = -1/2 + 1/4 =-1/4`
`3, -5/22 -1 +3/2-6/22 = (-5/22 - 6/22) -1+3/2 = -1/2 - 1+3/2 = -3/2 + 3/2 = 0 `
`4, -1/2 + 1/4 + 2/8 -11/77 = -1/2+1/4 +1/4 -11/77 = -1/2 +(1/4+1/4)-1/7 =-1/2 + 1/2 - 1/7 =0-1/7 = -1/7`
`5, 2/5 + 5/4+(-2/5+5/4)-5/2 = 2/5+5/4+-2/5+5/4-5/2 = (2/5+-2/5)+(5/4+5/4)-5/2 = 0+5/2-5/2 = 5/2 - 5/2 = 0`
1: =-3/7-4/7+5/13+8/13
=-1+1=0
2: =-5/14-2/14+1/4
=-1/2+1/4
=-1/4
3: =-5/22-6/22+3/2-1
=-1/2-1+3/2
=0
4: =-4/8+2/8+2/8-1/7=-1/7
5: =2/5+5/4-2/5+5/4-5/2
=5/2-5/2
=0
a) \(\left(\frac{4}{13}.\frac{6}{5}+\frac{4}{13}.\frac{2}{5}\right).\left(2x+1\right)^2=\frac{10}{13}\)
\(\left(\frac{4}{13}.\frac{8}{5}\right).\left(2x+1\right)^2=\frac{10}{13}\)
\(\frac{32}{65}.\left(2x+1\right)^2=\frac{10}{13}\)
\(\left(2x+1\right)^2=\frac{10}{13}\div\frac{32}{65}\)
\(\left(2x+1\right)^2=\frac{25}{16}\)
\(\Rightarrow2x+1\in\left\{\frac{5}{4};-\frac{5}{4}\right\}\)
\(\hept{\begin{cases}2x+1=\frac{5}{4}\\2x+1=-\frac{5}{4}\end{cases}\Rightarrow\hept{\begin{cases}2x=\frac{1}{4}\\2x=-\frac{9}{4}\end{cases}\Rightarrow}\hept{\begin{cases}x=\frac{1}{8}\\x=-\frac{9}{8}\end{cases}}}\)
Vậy \(x\in\left\{\frac{1}{8};-\frac{9}{8}\right\}\)
\(x^3-\frac{9}{16}.x=0\)
\(x\left(x^2-\frac{9}{16}\right)=0\)
\(\hept{\begin{cases}x=0\\x^2-\frac{9}{16}=0\end{cases}\Rightarrow\hept{\begin{cases}x=0\\x^2=\frac{9}{16}\end{cases}\Rightarrow}\hept{\begin{cases}x=0\\x=\pm\frac{3}{4}\end{cases}}}\)
Vậy \(x\in\left\{0;\frac{3}{4};-\frac{3}{4}\right\}\)
C1:
A = \(3\frac{5}{7}+4\frac{2}{3}\)\(-\left(2\frac{5}{7}+2\frac{1}{3}\right)\)
A = \(3\frac{5}{7}+4\frac{2}{3}\)\(-2\frac{5}{7}-2\frac{1}{3}\)
A = \(3\frac{5}{7}-2\frac{5}{7}+4\frac{2}{3}-2\frac{1}{3}\)
A = \(1+2\frac{1}{3}\)
A = \(1+\frac{7}{3}\)
A = \(\frac{10}{3}\)
C2:
A = \(3\frac{5}{7}+4\frac{2}{3}\)\(-\left(2\frac{5}{7}+2\frac{1}{3}\right)\)
A = \(\frac{26}{7}+\frac{14}{3}-\frac{19}{7}-\frac{7}{3}\)
A = \(1+\frac{14}{3}-\frac{7}{3}=\frac{10}{3}\)
C1: Ta có: \(B=8\frac{1}{9}-3\frac{2}{7}+6\frac{8}{7}-3\frac{5}{7}\)
\(=8+\frac{1}{9}-\left(3+\frac{2}{7}\right)+6+\frac{8}{7}-\left(3+\frac{5}{7}\right)\)
\(=8+\frac{1}{9}-3-\frac{2}{7}+6+1+\frac{1}{7}-3-\frac{5}{7}\)
= \(\left(8-3+6+1-3\right)+\left(\frac{1}{9}-\frac{2}{7}+\frac{1}{7}-\frac{5}{7}\right)\)
\(=9+\left(\frac{-47}{63}\right)\)
\(=\frac{520}{63}\)
C2: Đổi hỗn số ra phân số rồi tính ( cj nghĩ thế )
Bài 1: Tính nhanh:
A = 3/1*2 + 3/2*3 + 3/3*4 + ... + 3/399*400
=>3A = 1/1*2 + 1/2*3 + 1/3*4 + ... + 1/399*400
3A = 1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/399 - 1/400
3A = 1 - 1/400
3A = 400/400 - 1/400
3A = 399/400
A = 399/400 : 3
A = 399/400 . 1/3
A = 133/400.
Có gì ko hiểu bn ib mk nha.^^
\(A=\frac{3}{1.2}+\frac{3}{2.3}+\frac{3}{3.4}+...+\frac{3}{399.400}\)
\(A=3.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{399.400}\right)\)
\(A=3.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{399}-\frac{1}{400}\right)\)
\(A=3.\left(1-\frac{1}{400}\right)\)
\(A=3.\frac{399}{400}\)
\(A=\frac{1197}{400}\)
\(B=\frac{5}{1.2}+\frac{5}{2.3}+\frac{5}{3.4}+...+\frac{5}{399.400}\)
\(B=5.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{399.400}\right)\)
\(B=5.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{399}-\frac{1}{400}\right)\)
\(B=5.\left(1-\frac{1}{400}\right)\)
\(B=5.\frac{399}{400}\)
\(B=\frac{399}{80}\)
\(C=\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+...+\frac{2}{149.151}\)
\(C=\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{149}-\frac{1}{151}\)
\(C=\frac{1}{5}-\frac{1}{151}\)
\(C=\frac{146}{755}\)
\(D=\frac{3}{5.7}+\frac{3}{7.9}+\frac{3}{9.11}+...+\frac{3}{149.151}\)
\(D=\frac{3}{2}.\left(\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{9.11}+...+\frac{2}{149.151}\right)\)
\(D=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{9}-\frac{1}{11}+...+\frac{1}{149}-\frac{1}{151}\right)\)
\(D=\frac{3}{2}.\left(\frac{1}{5}-\frac{1}{151}\right)\)
\(D=\frac{3}{2}.\frac{146}{755}\)
\(D=\frac{219}{755}\)
\(E=\frac{11}{1.3}+\frac{11}{3.5}+\frac{11}{5.7}+...+\frac{11}{99.101}\)
\(E=\frac{11}{2}.\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{99.101}\right)\)
\(E=\frac{11}{2}.\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{99}-\frac{1}{101}\right)\)
\(E=\frac{11}{2}.\left(1-\frac{1}{101}\right)\)
\(E=\frac{11}{2}.\frac{100}{101}\)
\(E=\frac{550}{101}\)
_Chúc bạn học tốt_
\(a,\dfrac{1}{2}-\dfrac{1}{3}-\left(-\dfrac{5}{4}\right)=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{5}{4}=\dfrac{1\times6-1\times4+5\times3}{12}=\dfrac{6-4+15}{12}=\dfrac{17}{12}\\ b,\dfrac{5}{4}-\dfrac{1}{2}-\dfrac{7}{8}=\dfrac{5\times2-1\times4-7}{8}=\dfrac{10-4-7}{8}=-\dfrac{1}{8}\\ c,\dfrac{1}{5}-\dfrac{1}{2}+\dfrac{9}{10}=\dfrac{1\times2-1\times5+9}{10}=\dfrac{2-5+9}{10}=\dfrac{6}{10}=\dfrac{3}{5}\\ d,\dfrac{5}{4}-\dfrac{1}{3}+\dfrac{7}{6}=\dfrac{5\times3-1\times4+7\times2}{12}=\dfrac{15-4+14}{12}=\dfrac{25}{12}\)
`1/2+(-1/3)-(-5/4)`
`=1/2-1/3+5/4`
`=3/6-2/6+5/4`
`=1/6+5/4`
`=2/12+15/12`
`=17/12`
__
`5/4-1/2+(-7/8)`
`=5/4-1/2-7/8`
`=10/8-4/8-7/8`
`=6/8-7/8`
`=-1/8`
__
`1/5-1/2+9/10`
`=2/10-5/10+9/10`
`=-3/10+9/10`
`=6/10`
`=3/5`
__
`5/4-1/3+7/6`
`=15/12-4/12+14/12`
`=11/12+14/12`
`=25/12`
`#lv`