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`@` `\text {Ans}`
`\downarrow`
`1,`
`a)`
`-7/25 + (-8)/25`
`= (-7 - 8)/25`
`= -15/25`
`= -3/5`
`b)`
`6/13 + (-15)/39`
`= 18/39 + (-15)/39`
`= (18 - 15)/39`
`= 3/39`
`= 1/13`
`c)`
`5/7 + 4/(-14)`
`= 10/14 + (-4)/14`
`= (10 - 4)/14`
`= 6/14`
`= 3/7`
`d)`
`-8/18 + (-15)/27`
`= -4/9 + (-5)/9`
`= (-4-5)/9`
`= -9/9 = -1`
`2,`
`a)`
`3/5 + (-7)/4`
`= 12/20 + (-35)/20`
`= (12 - 35)/20`
`=-23/20`
`b)`
`(-2) + (-5)/8`
`= (-16)/8 + (-5)/8`
`= (-16 - 5)/8`
`= -21/8`
`c)`
`1/8 + (-5)/9`
`= 9/72 + (-40)/72`
`= (9-40)/72`
`= -31/72`
`d)`
`6/13 + (-14)/39`
`= 18/39 + (-14)/39`
`= (18 - 14)/39`
`= 4/39`
`e)`
`(-18)/24 + 15/21`
`= (-3)/4 + 5/7`
`= (-21)/28 + 20/28`
`= (-21 + 20)/28`
`= -1/28`
a: =35/17-18/17-9/5+4/5
=1-1=0
b: =-7/19(3/17+8/11-1)
=7/19*18/187=126/3553
c: =26/15-11/15-17/3-6/13
=1-6/13-17/3
=7/13-17/3=-200/39
1,
a,-3/5
b,-1/2
c,19/39
d,1/4
e,-39/40
f,-59/56
2,
a,=
b,<
c,>
d,<
k cho mình nha
a; \(\dfrac{9}{4}\) - \(\dfrac{-11}{4}\)
= \(\dfrac{9}{4}\) + \(\dfrac{11}{4}\)
= \(\dfrac{20}{4}\)
= 5
b; \(\dfrac{7}{8}\) - \(\dfrac{3}{-8}\) - \(\dfrac{1}{8}\)
= \(\dfrac{7}{8}\) + \(\dfrac{3}{8}\) - \(\dfrac{1}{8}\)
= \(\dfrac{7+3-1}{8}\)
= \(\dfrac{9}{8}\)
c; \(\dfrac{-5}{21}\) - \(\dfrac{25}{21}\) - \(\dfrac{-1}{21}\)
= \(\dfrac{-5}{21}\) - \(\dfrac{25}{21}\) + \(\dfrac{1}{21}\)
= \(\dfrac{-5-25+1}{21}\)
= \(\dfrac{-29}{21}\)
Bài 1: Ta chỉ cần bỏ ngoặc rồi cộng hai phân số để ra kết quả là số tự nhiên là xong
Bài 2:
A = \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+............+\frac{1}{2003.2004}\)
A = \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-.............-\frac{1}{2003}+\frac{1}{2003}-\frac{1}{2004}\)
A = \(1-\frac{1}{2004}\)
A = \(\frac{2004}{2004}-\frac{1}{2004}=\frac{2003}{2004}\)
Mk làm mẫu 1 bài nha
Bài 1 :
a, = (1/4+3/4) - (5/13+8/13)+2/11
= 1 - 1 + 2/11
= 2/11
Tk mk nha
Bài 3:
\(a.\dfrac{5}{3}+\left(7+\dfrac{-5}{3}\right)\\ =\dfrac{5}{3}+7+\dfrac{-5}{3}\\ =\left(\dfrac{5}{3}-\dfrac{5}{3}\right)+7\\ =7\\ b.\dfrac{-7}{31}+\left(\dfrac{24}{17}+\dfrac{7}{31}\right)\\ =\dfrac{-7}{31}+\dfrac{24}{17}+\dfrac{7}{31}\\ =\left(\dfrac{7}{31}-\dfrac{7}{31}\right)+\dfrac{24}{17}\\ =\dfrac{24}{17}\\ c.\dfrac{3}{7}+\left(\dfrac{-1}{5}+\dfrac{-3}{7}\right)\\ =\dfrac{3}{7}+\dfrac{-1}{5}+\dfrac{-3}{7}\\ =\left(\dfrac{3}{7}-\dfrac{3}{7}\right)+\dfrac{-1}{5}\\ =-\dfrac{1}{5}\)
Bài 2:
a: \(\dfrac{2}{7}+\dfrac{3}{7}=\dfrac{2+3}{7}=\dfrac{5}{7}\)
b: \(\dfrac{3}{8}+\dfrac{5}{8}=\dfrac{3+5}{8}=\dfrac{8}{8}=1\)
c: \(\dfrac{1}{7}+\dfrac{-4}{7}=\dfrac{1-4}{7}=-\dfrac{3}{7}\)
d: \(\dfrac{7}{-25}+\dfrac{-8}{25}=\dfrac{-7}{25}+\dfrac{-8}{25}=-\dfrac{15}{25}=-\dfrac{3}{5}\)
e: \(\dfrac{6}{18}+\dfrac{-14}{21}=\dfrac{1}{3}-\dfrac{2}{3}=-\dfrac{1}{3}\)
f: \(\dfrac{6}{13}+\dfrac{-14}{39}=\dfrac{18}{39}-\dfrac{14}{39}=\dfrac{4}{39}\)
g: \(-\dfrac{3}{21}+\dfrac{6}{42}=-\dfrac{3}{21}+\dfrac{3}{21}=0\)
h: \(\dfrac{7}{21}+\dfrac{9}{-36}=\dfrac{1}{3}-\dfrac{1}{4}=\dfrac{1}{12}\)
Bài 4:
a: \(\dfrac{6}{5}+\left(3+\dfrac{-1}{5}\right)\)
\(=\dfrac{6}{5}+3-\dfrac{1}{5}\)
=1+3=4
b: \(-\dfrac{3}{5}+\left(-\dfrac{2}{5}+2\right)\)
\(=-\dfrac{3}{5}-\dfrac{2}{5}+2=2-1=1\)
c: \(-\dfrac{3}{5}+\left(-\dfrac{2}{5}+2\right)\)
\(=-\dfrac{3}{5}-\dfrac{2}{5}+2\)
=2-1=1
d: \(-\dfrac{5}{11}+\left(-\dfrac{6}{11}+1\right)\)
\(=-\dfrac{5}{11}-\dfrac{6}{11}+1=1-1=0\)
e: \(-\dfrac{17}{13}+\left(\dfrac{25}{101}+\dfrac{4}{13}\right)\)
\(=-\dfrac{17}{13}+\dfrac{4}{13}+\dfrac{25}{101}\)
\(=-1+\dfrac{25}{101}=-\dfrac{76}{101}\)