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CM
30 tháng 12 2017
a, x - 3 : 2 = 5 14 : 5 12
=> x - 3 : 2 = 5 2
=> x - 3 : 2 = 25
=> x – 3 = 25
=> x = 53
b, 30 : x - 7 = 15 19 : 15 18
=> 30 : x - 7 = 15
=> x – 7 = 2
=> x = 9
c, x 70 = x
=> x 70 - x = 0
=> x ( x 69 - 1 ) = 0
=> 
d, 2 x + 1 3 = 9 . 81
=> 2 x + 1 3 = 9 3
=> 2x + 1 = 9
=> x = 4
e, 5 x + 5 x + 2 = 650
=> 5 x 1 + 5 2 = 650
=> 5 x . 26 = 650
=> 5 x = 25
=> x = 2
f, 4 x - 1 2 = 25 . 9
=> 4 x - 1 2 = 5 2 . 3 2
=> 4 x - 1 2 = 15 2
=> 4x – 1 = 15
=> x = 4
CM
3 tháng 3 2019
b) x 70 = x
x 70 – x = 0
x . ( x 69 – 1) = 0
x = 0 hoặc x 69 – 1 = 0
x = 0 hoặc x 69 = 1
x = 0 hoặc x = 1
PT
1
CM
19 tháng 4 2018
a) 2 5 + − 3 7 = x 70
− 1 35 = x 70 − 2 70 = x 70 ⇒ x = − 2
b) 5 6 + − 19 30 = 1 x
1 5 = 1 x ⇒ x = 5
PT
1
PT
1
CM
27 tháng 6 2018
a) 2 5 + − 3 7 = x 70 ⇔ − 1 35 = x 70 ⇔ − 2 70 = x 70 ⇔ x = − 2
b) 5 6 + − 19 30 = 1 x ⇔ 6 30 = 1 x ⇔ 1 5 = 1 x ⇔ x = 5
LH
0
MT
8 tháng 4 2020
\(a,-152-\left(3x+1\right)=\left(-2\right).\left(-77\right)\)
\(-152-\left(3x+1\right)=154\)
\(3x+1=-152-154\)
\(3x=306\)
\(x=-102\)
Vậy \(x=-102\)
\(b,234+\left(-334-x\right)=500\)
\(-334-x=266\)
\(x=-600\)
Vậy \(x=-600\)
\(c,\left(567-x\right)+121=-641\)
\(567-x=-762\)
\(x=1329\)
Vậy \(x=1329\)
MT
8 tháng 4 2020
Làm lại câu a :
a, -152-(3x+1)=(-2).(-77)
-152-(3x+1)=154
3x+1=-306
3x=-307
x=-307/3
Vậy x=-307/3
H9
HT.Phong (9A5)
CTVHS
9 tháng 1
a) \(\dfrac{2x+5}{2x+1}=\dfrac{2x+1+4}{2x+1}=\dfrac{2x+1}{2x+1}+\dfrac{4}{2x+1}=1+\dfrac{4}{2x+1}\)
Để \(\dfrac{2x+5}{2x+1}\in Z\) thì \(\dfrac{4}{2x+1}\in Z\)
\(\Rightarrow4\) ⋮ \(2x+1\)
\(\Rightarrow2x+1\inƯ\left(4\right)=\left\{1;-1;2;-2;4;-4\right\}\)
\(\Rightarrow2x\in\left\{0;-2;1;-3;3;-5\right\}\)
\(\Rightarrow x\in\left\{0;-1;\dfrac{1}{2};-\dfrac{3}{2};\dfrac{3}{2};-\dfrac{5}{2}\right\}\)
Mà x nguyên \(\Rightarrow\text{x}\in\left\{0;-1\right\}\)
b) \(\dfrac{3x+5}{x+1}=\dfrac{3x+3+2}{x+1}=\dfrac{3\left(x+1\right)+2}{x+1}=\dfrac{3\left(x+1\right)}{x+1}+\dfrac{2}{x+1}=3+\dfrac{2}{x+1}\)
Để \(\dfrac{3x+5}{x+1}\in Z\) thì \(\dfrac{2}{x+1}\in Z\)
\(\Rightarrow2\) ⋮ \(x+1\)
\(\Rightarrow x+1\inƯ\left(2\right)=\left\{1;-1;2;-2\right\}\)
\(\Rightarrow x\in\left\{0;-2;1;-3\right\}\)
c) \(\dfrac{3x+8}{x-1}=\dfrac{3x-3+11}{x-1}=\dfrac{3\left(x-1\right)+11}{x-1}=\dfrac{3\left(x-1\right)}{x-1}+\dfrac{11}{x-1}=3+\dfrac{11}{x-1}\)
Để: \(\dfrac{3x+8}{x-1}\in Z\) thì \(\dfrac{11}{x-1}\in Z\)
\(\Rightarrow11\) ⋮ \(x-1\)
\(\Rightarrow x-1\inƯ\left(11\right)=\left\{1;-1;11;-11\right\}\)
\(\Rightarrow x\in\left\{2;0;12;-10\right\}\)
d) \(\dfrac{5x+12}{x-2}=\dfrac{5x-10+22}{x-2}=\dfrac{5\left(x-2\right)+22}{x-2}=\dfrac{5\left(x-2\right)}{x-2}+\dfrac{22}{x-2}=5+\dfrac{22}{x-2}\)
Để: \(\dfrac{5x+12}{x-2}\in Z\) thì \(\dfrac{22}{x-2}\in Z\)
\(\Rightarrow22\) ⋮ \(x-2\)
\(\Rightarrow x-2\inƯ\left(22\right)=\left\{1;-1;2;-2;11;-11;22;-22\right\}\)
\(\Rightarrow x\in\left\{3;1;4;0;13;-9;24;-20\right\}\)
e) \(\dfrac{7x-12}{x+16}=\dfrac{7x+112-124}{x+16}=\dfrac{7\left(x+16\right)-124}{x+16}=\dfrac{7\left(x+16\right)}{x+16}-\dfrac{124}{x+16}=7-\dfrac{124}{x+16}\)
Để \(\dfrac{7x-12}{x+16}\in Z\) thì \(\dfrac{124}{x+16}\in Z\)
\(\Rightarrow124\) ⋮ \(x+16\)
\(\Rightarrow x+16\inƯ\left(124\right)=\left\{1;-1;2;-2;4;-4;31;-31;62;-62;124;-124\right\}\)
\(\Rightarrow x\in\left\{-15;-17;-14;-18;-12;-20;15;-47;46;-78;108;-140\right\}\)
70+8(3x-12)=334
8(3x-12)=334-70=264
3x-12=264:8=33
3x=33+12=45
x=45:3=15
70+8(3x-12)=334
8(3x-12)=334-70
8(3x-12)=264
3x-12 =264:8
3x-12=33
3x=33+12
3x=45
x=45:3
x=15