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2/3.x + 1/4 = 7/12
2/3.x = 7/12 - 1/4
2/3.x = 1/3
x = 1/3 : 2/3
x = 1/2
Bài làm
\(\frac{2}{3}x+\frac{1}{4}=\frac{7}{12}\)
\(\frac{2}{3}x=\frac{7}{12}-\frac{1}{4}\)
\(\frac{2}{3}x=\frac{7}{12}-\frac{3}{12}\)
\(\frac{2}{3}x=\frac{4}{12}\)
\(\frac{2}{3}x=\frac{1}{3}\)
\(x=\frac{1}{3}:\frac{2}{3}\)
\(x=\frac{1}{3}.\frac{3}{2}\)
\(x=\frac{1}{2}\)
Vậy \(x=\frac{1}{2}\)
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
\(\Leftrightarrow3^x=5.3^{12}+4.\left(3^3\right)^4=5.3^{12}+4.3^{12}.\)
\(\Leftrightarrow3^x=9.3^{12}=3^2.3^{12}=3^{14}\Leftrightarrow x=14\)
a: =152,3+7,7+2021,19-2021,19
=160
b: =7/15*3/14*20/13
\(=\dfrac{7}{14}\cdot\dfrac{3}{15}\cdot\dfrac{20}{13}=\dfrac{1}{2}\cdot\dfrac{1}{5}\cdot\dfrac{20}{13}=\dfrac{2}{13}\)
c: \(=\dfrac{7}{4}\left(\dfrac{13}{12}-\dfrac{10}{12}\right)+\dfrac{5}{6}=\dfrac{7}{16}+\dfrac{5}{6}=\dfrac{61}{48}\)
\(\frac{4^8.3^{12}.27^2}{6^{12}.9^3}\)
= \(\frac{\left(2^2\right)^8.3^{12}.27^2}{\left(2.3\right)^{12}.\left(3^2\right)^3}\)
= \(\frac{2^{16}.3^{12}.27^2}{2^{12}.3^{12}.27^2}\)
= \(\frac{2^{16}}{2^{12}}\)= 24 = 16
\(\frac{x-12}{3}=\frac{x+1}{4}\)
=>(x-12).4=(x+1)*3
4x-48=3x+3
4x-3x=48+3
x=51
(x-12)/3=(x+1)/4
(x-12)*4=(x+1)*3
x*4-12*4=x*3+1*3
4x-48=3x+3
4x-3x=3+48
x=51
1) 673+x=3x-(x-12)
673+x=3x-x+12
673+x=2x+12
673+x-2x-12=0
661-x=0
x=661
2)25-(x-27)=-18-(x-9)
25-x+27=-18-x+9
52-x=-9-x
52-x+9+x=0
61=0(vô lý)
3)x-(20-x)=36
x-20+x=36
2x=36+20
2x=56
=> x=28
4)x-(-18-2x)=-33
x+18+2x=-33
3x+18=-33
3x=-33-18
3x=-51
=> x=-17
= (12-12) + (11+10) - (9+8) - (7+5) - (4+3) + (2-1)
= 0 + 21 - 17 - 12 - 7 + 1
= 21- 17 - 12 - 7 +1
= 4 - 12 - 7 +1
= -8 - 7 + 1
= -15 + 1
= -14
hết
= 12 - 12 + 11 + ( 10 - 9 ) + ( 8 - 7 ) + ( 5 - 4 ) + 3 + ( 2 -1 )
= 0 + 11 + 1 + 1 + 1 + 3 + 1
= 11 +1 + 1 + 1 + 3 + 1
= 12 + 1 + 1 + 3 + 1
= 13 + 1 + 3 + 1
= 14 + 3 + 1
= 17 + 1
= 18
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\(x+2=9\Leftrightarrow x=7\)