1/4 x 12/13 + 1/6 x 12/13 + 1/8 x 12/13=?
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câu a) lấy mẫu số chung cộng với nhau
câu b) lấy 1 để ngoài nhân r 1/2-1/3 rồi tương tự
Bài 1:
a: \(x=\dfrac{2}{3}:\dfrac{3}{5}=\dfrac{2}{3}\cdot\dfrac{5}{3}=\dfrac{10}{9}\)
b: \(x=\dfrac{17}{8}:\dfrac{7}{17}=\dfrac{17}{8}\cdot\dfrac{17}{7}=\dfrac{289}{56}\)
c: \(x=-\dfrac{3}{4}:\dfrac{7}{12}=\dfrac{-3}{4}\cdot\dfrac{12}{7}=\dfrac{-63}{28}=-\dfrac{9}{4}\)
d: \(\Leftrightarrow x\cdot\dfrac{1}{6}=\dfrac{3}{8}-\dfrac{1}{4}=\dfrac{1}{4}\)
hay \(x=\dfrac{1}{4}:\dfrac{1}{6}=\dfrac{3}{2}\)
e: \(\Leftrightarrow\dfrac{1}{2}:x=-4-\dfrac{1}{3}=-\dfrac{17}{3}\)
hay \(x=-\dfrac{1}{2}:\dfrac{17}{3}=\dfrac{-3}{34}\)
`x/8 = 3/4 +(-5/8)`
`=>x/8 = 6/8 +(-5/8)`
`=>x/8 = 1/8`
`=>x=1`
`-----`
`x/12 =3/4 +(-2/3)`
`=>x/12 = 9/12 + (-8/12)`
`=> x/12=1/12`
`=>x=1`
`----`
`1+11/13=24/x`
`=> 13/13 +11/13=24/x`
`=> 24/13 =24/x`
`=>x=13`
`----`
`x/6 -3/4=1/12`
`=>x/6 = 1/12 +3/4`
`=>x/6 = 1/12 + 9/12`
`=>x/6 = 10/12`
`=>x/6= 5/6`
`=>x=5`
a) \(\dfrac{-5}{9}-\dfrac{-5}{12}=\dfrac{-5}{9}+\dfrac{5}{12}=\dfrac{-20}{36}+\dfrac{15}{36}=-\dfrac{5}{36}\)
b) \(\dfrac{-5}{12}:\dfrac{15}{4}=\dfrac{-5}{12}\times\dfrac{4}{15}=\dfrac{-1}{9}\)
c) \(\dfrac{1}{13}\cdot\dfrac{8}{13}+\dfrac{5}{13}\cdot\dfrac{1}{13}-\dfrac{14}{13}=\dfrac{1}{13}\cdot\left(\dfrac{8}{13}+\dfrac{5}{13}\right)-\dfrac{14}{13}=\dfrac{1}{13}\cdot1-\dfrac{14}{13}=\dfrac{1}{13}-\dfrac{14}{13}=-1\)
1) = \(\frac{3}{5}\)
2) =\(\frac{6}{7}\)
3)\(\frac{9}{13}\)
4)\(\frac{4}{13}\)
9/13 x 7/12 + 9/13 x 5/12 - 9/13
= 9/13 x (7/12 + 5/12 - 1)
= 9/13 x 0
= 0
4/13 x 5/12 + 4/13 x 7/12 - 4/3
= 4/13 x (5/12 + 7/12) - 4/3
= 4/13 x 1 - 4/3
= 4/13 - 4/3
= -40/39
1/4 x 12/13 + 1/6 x 12/13 + 1/8 x 12/13
= 12/13 x (1/4 + 1/6 + 1/8 )
= 12/13 x 13/14
= 1/2
1/4 x 12/13 + 1/6 x 12/13 + 1/8 x 12/13= 0.5
hok tốt