12 . (x - 1) : 3 =4³ + 2³
giúp em với ạ :3
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a) \(\dfrac{13}{20}+\dfrac{3}{5}+x=\dfrac{5}{6}\)
\(\Rightarrow\dfrac{5}{4}+x=\dfrac{5}{6}\)
\(\Rightarrow x=\dfrac{5}{6}-\dfrac{5}{4}\)
\(\Rightarrow x=\dfrac{-5}{12}\)
b) \(x+\dfrac{1}{3}=\dfrac{2}{5}-\dfrac{-1}{3}\)
\(\Rightarrow x+\dfrac{1}{3}=\dfrac{11}{15}\)
\(\Rightarrow x=\dfrac{11}{15}-\dfrac{1}{3}\)
\(\Rightarrow x=\dfrac{2}{5}\)
c)\(\dfrac{-5}{8}-x=\dfrac{-3}{20}-\dfrac{-1}{6}\)
\(\dfrac{-5}{8}-x=\dfrac{1}{60}\)
\(\Rightarrow x=\dfrac{-5}{8}-\dfrac{1}{60}\)
\(\Rightarrow x=\dfrac{-77}{120}\)
d) \(\dfrac{3}{5}-x=\dfrac{1}{4}+\dfrac{7}{10}\)
\(\Rightarrow\dfrac{3}{5}-x=\dfrac{19}{20}\)
\(\Rightarrow x=\dfrac{3}{5}-\dfrac{19}{20}\)
\(\Rightarrow x=\dfrac{-7}{20}\)
e) \(\dfrac{-3}{7}-x=\dfrac{4}{5}+\dfrac{-2}{3}\)
\(\Rightarrow\dfrac{-3}{7}-x=\dfrac{2}{15}\)
\(\Rightarrow x=\dfrac{-3}{7}-\dfrac{2}{15}\)
\(\Rightarrow x=\dfrac{-59}{105}\)
g) \(\dfrac{-5}{6}-x=\dfrac{7}{12}+\dfrac{-1}{3}\)
\(\Rightarrow\dfrac{-5}{6}-x=\dfrac{1}{4}\)
\(\Rightarrow x=\dfrac{-5}{6}-\dfrac{1}{4}\)
\(\Rightarrow x=\dfrac{-13}{12}\)
a: \(\Leftrightarrow4\left(2x+1\right)-3\left(6x-1\right)=2x+1\)
=>8x+4-18x+3=2x+1
=>-10x+7=2x+1
=>-12x=-6
hay x=1/2
b: \(\Leftrightarrow4x^2-12x+7x-21-x^2=3x^2+6x\)
=>5x-21=6x
=>-x=21
hay x=-21
a) B = \(\dfrac{4}{3}.\dfrac{5}{4}....\dfrac{21}{20}=\dfrac{1}{3}.1.....\dfrac{21}{1}=\dfrac{21}{3}=7\)
b) Em chịu, chưa học số âm :)
a, \(\frac{x}{12}=-\frac{1}{24}-\frac{1}{8}\Leftrightarrow\frac{x}{12}=-\frac{1}{6}\Leftrightarrow6x=-12\Leftrightarrow x=-2\)
b, \(\frac{2}{3}x=\frac{1}{2}x+\frac{15}{12}\Leftrightarrow\frac{2x}{3}=\frac{x}{2}+\frac{15}{12}\Leftrightarrow\frac{4x}{6}-\frac{3x}{6}=\frac{15}{12}\Leftrightarrow\frac{x}{6}=\frac{15}{12}\Leftrightarrow x=\frac{15}{2}\)
c, \(\left|\frac{3}{4}-2x\right|+\frac{1}{6}=\frac{9}{2}\Leftrightarrow\left|\frac{3}{4}-2x\right|=\frac{13}{3}\)
\(\Leftrightarrow\orbr{\begin{cases}\frac{3}{4}-2x=\frac{13}{3}\\\frac{3}{4}-2x=-\frac{13}{3}\end{cases}\Leftrightarrow\orbr{\begin{cases}2x=-\frac{43}{12}\\2x=\frac{61}{12}\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=-\frac{43}{24}\\x=\frac{61}{24}\end{cases}}}\)
( 2 x y + 2/15 ) x 3 = 4/5
( 2 x y + 2/15 ) = 4/5 : 3
( 2 x y + 2/15 ) = 4/15
2 x y = 4/15 - 2/15
2 x y = 2/15
y = 2/15 :2
y = 1/15
(2 x y + 2/15) x 3 = 4/5
2 x y + 2/15) = 4/5 : 3
2 x y + 2/15 = 4/15
2 x y = 4/15 - 2/15
2 x y = 2/15
y = 2/15 : 2
y = 1/15
7/9 x (2 - 1/3 x y) = 14/15
(2 - 1/3 x y) = 14/15 : 7/9
(2 - 1/3 x y) = 6/5
2 - y = 6/5 x 1/3
2 - y = 2/5
y = 2/5 + 2
y = 12/5
4/21 + 5 x y - 8/7 = 1/3
4/21 + 5 x y = 1/3 + 8/7
4/21 + 5 x y = 31/21
5 x y = 31/21 - 4/21
5 x y = 9/7
y = 9/7 : 5
y = 9/35
7/12 x y - 3/12 x y = 5
y x (7/12 - 3/12) = 5
y x 1/3 = 5
y = 5 : 1/3
y = 15
Bài làm
12 . (x - 1) : 3 = 43 + 23
12 . (x - 1) : 3 = 64 + 8
12 . ( x - 1) : 3 = 72
12 . (x - 1) = 72 . 3
12 . (x - 1) = 216
x - 1 = 216 : 12
x - 1 = 18
x = 18 + 1
x = 19
Vậy x = 19
`12.(x-1):3=4^{3}+2^{3}`
`=>4(x-1)=64+8=72`
`=>x-1=72:4=18`
`=>x=18+1`
`=>x=19`