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\(121-5.\left(60-5x\right)=21^{10}:\left(21^6.21^3\right)\)
\(121-5.\left(60-5x\right)=21^{10}:21^9\)
\(121-5.\left(60-5x\right)=21\)
\(5.\left(60-5x\right)=121-21\)
\(5.\left(60-5x\right)=100\)
\(60-5x=100:5\)
\(60-5x=20\)
\(5x=60-20\)
\(5x=20\)
\(\Rightarrow x=4\)
\(121-5.\left(60-5x\right)=21^{10}:\left(21^6.21^3\right)\)
\(121-300+25x=21^{10}:21^{11}\)
\(25x-179=\frac{1}{21}\)
\(25x=\frac{1}{21}+179\)
\(25x=\frac{3760}{21}\)
\(x=\frac{3760}{21}:25\)
\(x=\frac{752}{105}\)
vay \(x=\frac{752}{105}\)
Bài 1:
a: x/-2=-18/x
=>x2=36
=>x=6 hoặc x=-6
b: x/2+x/5=17/10
=>7/10x=17/10
hay x=17/7
Bài 1:
a) \(\frac{16}{15}.\frac{\left(-5\right)}{14}.\frac{54}{24}.\frac{56}{21}\)
\(=\frac{4.2.2}{5.3}.\frac{\left(-5\right)}{2.7}.\frac{3.3}{4}.\frac{8}{3}\)
\(=\frac{4.2.2.\left(-5\right).3.3.8}{5.3.2.7.4.3}\)
\(=\frac{-16}{7}\)
b) \(\frac{7}{3}.\frac{\left(-5\right)}{2}.\frac{15}{21}.\frac{4}{\left(-5\right)}\)
\(=\frac{7}{3}.\frac{\left(-5\right)}{2}.\frac{5}{7}.\frac{2.2}{\left(-5\right)}\)
\(=\frac{7.\left(-5\right).5.2.2}{3.2.7.\left(-5\right)}\)
\(=\frac{10}{3}\)
Bài 2:
a) \(\frac{21}{24}.\frac{11}{9}.\frac{5}{7}=\frac{7}{8}.\frac{11}{9}.\frac{5}{7}=\frac{11.5}{8.9}=\frac{55}{72}\)
b) \(\frac{5}{23}.\frac{17}{26}+\frac{5}{23}.\frac{9}{26}\)
\(=\frac{5}{23}.\left(\frac{17}{26}+\frac{9}{26}\right)=\frac{5}{23}.1=\frac{5}{23}\)
c) \(\left(\frac{3}{29}-\frac{1}{5}\right).\frac{29}{3}=\frac{3}{29}.\frac{29}{3}-\frac{1}{5}.\frac{29}{3}\)
\(=1-1\frac{14}{15}=\frac{14}{15}\)
Bài 3:
a) x/5 = 2/5
=> x =2
b) -4/x = 20/14 = 10/7
=> -4/x = 10/7
=> x.10 = (-4).7
x.10 = - 28
x= -28 :10
x= -2,8
c) 4/7 = 12/x = 12/ 21
=> 12/x = 12/21
=> x = 21
d) 3/7 = x / 21 = 9/21
=> x/21 = 9/21
=> x= 9
a) 2/3 x + 1/2 = 1/10
2/3 x = 1/10 - 1/2
2/3 x = -2/5
x = -2/5 : 2/3
x = -3/5
b) 2/3 x + 1/5 = 7/10
2/3 x = 7/10 - 1/5
2/3 x = 1/2
x = 1/2 : 2/3
x = 3/4
c) (3 4/5 - 2x) . 1 1/3 = 5
19/5 - 2x = 5 : 4/3
19/5 - 2x = 15/4
2x = 19/5 - 15/4
2x = 1/20
x = 1/20 : 2
x = 1/40
d) x/7 = 6/(-21)
x = 6.7/(-21)
x = -2
a) | 5/4x -7/2| - | 5/8x + 3/5| = 0
|5/4x - 7/2| = | 5/8x + 3/5|
TH1: 5/4x - 7/2 = 5/8x + 3/5
=> 5/4x - 5/8x = 3/5 +7/2
5/8x = 41/10
x = 41/10:5/8
x = 164/25
TH2: 5/4x - 7/2 = -5/8x - 3/5
=> 5/4x + 5/8x = -3/5 +7/2
15/8x = 29/10
x = 29/10 : 15/8
x = 116/75
KL: x = 164/25 hoặc x = 116/75
các bài cn lại b lm tương tự nha! h lm dài lắm!
\(x+\frac{2}{5}=\frac{-1}{3}\) \(\frac{5}{7}-x=\frac{-9}{21}\)
\(x=\frac{-1}{3}-\frac{2}{5}\) \(x=\frac{5}{7}-\frac{-9}{21}\)
\(x=\frac{-11}{15}\) \(x=\frac{8}{7}\)
x+2/5=-1/3
=>x=-1/3-2/5
=>x=-11/15
5/7-x=-9/21
=>x=5/7-(-9/21)
=>x=8/7
Lời giải:
a.
$x=\frac{7}{25}+\frac{-1}{5}=\frac{7}{25}+\frac{-5}{25}=\frac{7-5}{25}=\frac{2}{25}$
b.
$x=\frac{5}{11}+\frac{4}{-9}=\frac{5}{11}-\frac{4}{9}=\frac{45}{99}-\frac{44}{99}=\frac{1}{99}$
c.
$\frac{x}{-1}=\frac{-1}{3}-\frac{5}{9}=\frac{-3}{9}-\frac{5}{9}=\frac{-8}{9}$
$x=(-1).\frac{-8}{9}=\frac{8}{9}$
\(\left(x-3\right)\left(21+5\right)=5\)
\(\Leftrightarrow\left(x-3\right).26=5\)
\(\Leftrightarrow x-3=\frac{5}{26}\)
\(\Leftrightarrow x=\frac{83}{26}\)
Vậy \(x=\frac{83}{26}\)
83/26 nha ban