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\(\frac{10^{18}}{2^{18}}=\frac{\left(2.5\right)^{18}}{2^{18}}=\frac{2^{18}.5^{18}}{2^{18}}=5^{18}\)

vậy 5^x.5^x+1.5^x+2=5^{x+(x+1)+(x+2)}<5¹⁸=>x+(x+1)+(x+2) <18

vậy 3x+3<18 thì3x<15 =>x<5 

x <5 vay65 x thuộc 1;2;3;4

vậy x=1;2;3;4

X=1;2;3;4

\(\frac{10^{18}}{2^{18}}=\frac{\left(2.5\right)^{18}}{2^{18}}=\frac{2^{18}.5^{18}}{2^{18}}=5^{18}\)

Vậy 5^x.5^x+1.5^x+2=5^{x+(x+1)-(x+2)}<5¹⁸

=> x+(x+1)-(x+2)<18

Vậy 3x+3<18 thì 3x<15 

=> x<5

Vậy x={ 1;2;3;4}

\(\dfrac{x+1}{x-5}+\dfrac{x-18}{x-5}+\dfrac{x+2}{x-5}\)

\(=\dfrac{x+1+x-18+x+2}{x-5}\)

\(=\dfrac{3x-15}{x-5}\)

\(=\dfrac{3\left(x-5\right)}{x-5}\)

\(=\dfrac{3}{1}\)

\(=3\)

\(\dfrac{x+1}{x-5}+\dfrac{x-18}{x-5}+\dfrac{x+2}{x-5}\\ =\dfrac{x+1+x-18+x+2}{x-5}\\ =\dfrac{\left(x+x+x\right)+\left(1-18+2\right)}{x-5}\\ =\dfrac{3x-15}{x-5}=\dfrac{3\left(x-5\right)}{x-5}=3\)

a, \(x-\frac{2}{5}=\frac{5}{7}\)

\(x=\frac{5}{7}+\frac{2}{5}\)

\(x=\frac{39}{35}\)

b, \(\frac{5}{12}-x=\frac{7}{18}\)

\(x=\frac{5}{12}-\frac{7}{18}\)

\(x=\frac{1}{36}\)

x-2/5=-5/2

x=-5/2+2/5

x=-21/10

vậy x=21/10

5/12-x=7/18

x=5/12-7/18

x=1/36

vậy x=1/35

câu b mình sai nên mình làm lại

5/12-x=7/18

x=5/12-7/18

x=1/36

vậy x=1/36

5^18 = 5^5-x

=> 18 = 5-x

=> x = 5 - 18 = -13

Vậy,......

sorry sai nha....

\(5^{18}=\frac{5^5}{5^x}\Rightarrow5^{18+x}=5^5\Rightarrow18+x=5\Rightarrow x=-13\)

giúp !!! 

Tính lần lượt 2 vế ta được:

-5 < x< -0,4

=> x = -4, -3, -2, -1, 0

\(=\frac{x+1+x-18+x+2}{x-5}\)

\(=\frac{3x-15}{x-5}=\frac{3\left(x-5\right)}{x-5}=3\)

\(\frac{x-15}{x-5}\)