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\(\Rightarrow5^x\left(1+5^2+5^3\right)=31\\ \Rightarrow5^x\cdot31=31\\ \Rightarrow5^x=1=5^0\Rightarrow x=0\)
a: =7/8:(2/9-18+1/36)-5/12
=-7/142-5/12=-397/852
b: =3/7(4/9+5/9:6/12)=2/3
c: =5^8(16/31-47/31)+1/3=-5^8+1/3
d: =7/2(3/8+5/8:4/15)=609/64
31) 1/2.x+3/5.(x-2)=3
1/2x + 3/5x - 6/5 = 3
x(1/2 + 3/5) = 3 + 6/5
x.11/10 = 21/5
x=21/5 : 11/10
x = 42/11
Bài 1:
Ta có: \(x-35\%\cdot x=\dfrac{1}{25}\)
\(\Leftrightarrow65\%\cdot x=\dfrac{1}{25}\)
\(\Leftrightarrow x=\dfrac{1}{25}:\dfrac{13}{20}=\dfrac{1}{25}\cdot\dfrac{20}{13}=\dfrac{4}{65}\)
Vậy: \(x=\dfrac{4}{65}\)
Bài 2:
a) Ta có: \(17\dfrac{2}{31}-\left(\dfrac{15}{17}+6\dfrac{2}{31}\right)\)
\(=17\dfrac{2}{31}-\dfrac{15}{17}-6\dfrac{2}{31}\)
\(=11+\dfrac{2}{31}-\dfrac{15}{17}\)
\(=\dfrac{5366}{527}\)
a)(x+28):13=25,2
x+28=25,2.13
x+28=327,6
x=327,6-28
x=299,6
b)(7x+6)*5^5=5^8
7x+6=5^8:5^5
7x+6=5^3
7x+6=125
7x=125-6
7x=119
x=119:7
x=17
c)(x-3)^2-23=2
(x-3)^2=2+23
(x-3)^2=25
x-3=5
x=5+3
x=8
d)3^30(x-2)=(3^32-3^31)
3^30(x-2)=3^1
x-2=3^1:3^30
x-2=3-29
x=3-29+2
=>x-2=2
hay x=4