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bài 1:
a) 1/3x=-5/3
x=-5
b) x+12/5=37/15
x=1/15
c) x-1/7=-36/7
x=-5
d) 3x-1/2=0
3x=1/2
x=1/6
e) 2/5+x=1/4
x=-3/20
a) 3/5 x=4/7+1/5; b)(2x-1/2):3=12;
3/5 x=27/35 (2x-1/2)=12x3
x=27/35:3/5 2x-1/2=36
x=9/7 2x=36+1/2
Vay x=9/7 2x=73/2
x=73/2:2
x=73/4
Vay x=73/4
a; - \(\dfrac{10}{13}\) + \(\dfrac{5}{17}\) - \(\dfrac{3}{13}\) + \(\dfrac{12}{17}\) - \(\dfrac{11}{20}\)
= - (\(\dfrac{10}{13}\) + \(\dfrac{3}{13}\)) + (\(\dfrac{5}{17}\) + \(\dfrac{12}{17}\)) - \(\dfrac{11}{20}\)
= - 1 + 1 - \(\dfrac{11}{20}\)
= 0 - \(\dfrac{11}{20}\)
= - \(\dfrac{11}{20}\)
b; \(\dfrac{3}{4}\) + \(\dfrac{-5}{6}\) - \(\dfrac{11}{-12}\)
= \(\dfrac{9}{12}\) - \(\dfrac{10}{12}\) + \(\dfrac{11}{12}\)
= \(\dfrac{10}{12}\)
= \(\dfrac{5}{6}\)
c; [13.\(\dfrac{4}{9}\) + 2.\(\dfrac{1}{9}\)] - 3.\(\dfrac{4}{9}\)
= [\(\dfrac{52}{9}\) + \(\dfrac{2}{9}\)] - \(\dfrac{4}{3}\)
= \(\dfrac{54}{9}\) - \(\dfrac{4}{3}\)
= \(\dfrac{14}{3}\)
a) (x + 5/6) . 12/5 - 5/4 = 35%
=> (x + 5/6) . 12/5 = 7/20 + 5/4
=> (x + 5/6) . 12/5 = 8/5
=> x + 5/6 = 8/5 : 12/5
=> x + 5/6 = 2/3
=> x = 2/3 - 5/6
=> x = -1/6
b) 3.(x - 1/2) - 5.(x + 3/5) = -x + 1/5
=> 3x - 3/2 - 5x - 3 = -x + 1/5
=> -2x - 9/2 = -x + 1/5
=> -2x + x = 1/5 + 9/2
=> -x = 47/10
=> x = -47/10
c) 5/2 - 3.(1/3 - x) = 1/4 - 7x
=> 5/2 - 1 + 3x = 1/4 - 7x
=> 3/2 + 3x = 1/4 - 7x
=> 3/x + 7x = 1/4 - 3/2
=> 10x = -5/4
=> x = -5/4 : 10
=> x = -1/8
d) 1/2x + 4/5 .(5/2 + x) = 15/4
=> 1/2x + 2 + 4/5x = 15/4
=> 13/10x = 15/4 - 2
=> 13/10x = 7/4
=> x = 7/4 : 13/10
=> x= 35/26
a ) 18^2 : 9^2 .2^2 +12-12:3
= 4^2 :3 = 16/3
b) 5! +2^10 :2^8
= 120 + 4 = 124
c)28 :[ 117 - ( 117- 4) ] . 7 + 5^3 :125
= 28 : 4 * 7 + 1 = 50
d)3^3. 3^5.3 +2^7 :64
= 3^9 + 2^7 : 2^6 = 3^9 + 1 (tính nhé)
bài 2: tìm x thuôc N biết
a) (2x -2^5). 5^3=2^3.5^3
2x - 2^5 = 2^3
2x = 40
x=20
b) 2^2x -4= 72:3^2
2^2 * x = 12
x= 3
c)3^x + 3^x+1 =108
\(3^x+3^{x+1}=108\) (là thế này ak??)
3^x (1+3) = 108
3^x = 27
x=3
d)(x -3).(3x+5) =0
\(\Rightarrow\orbr{\begin{cases}x-3=0\\3x+5\end{cases}\Rightarrow\orbr{\begin{cases}x=3\\x=-\frac{5}{3}\end{cases}}}\)
a,
Ta có:
\(\frac{11}{12}-\left(\frac{2}{5}+x\right)=\frac{2}{3}\)
\(\Leftrightarrow\frac{55}{60}-\frac{60\left(\frac{2}{5}+x\right)}{60}=\frac{40}{60}\)
\(\Leftrightarrow\frac{55}{60}-\frac{24+60x}{60}=\frac{40}{60}\)
=> 55-24-60x=40
<=> 31-60x=40
<=> x=-3/20
Mấy câu còn lại cũng tương tự thế đó
Đáp án cần chọn là: B
x + 2 3 = − 1 12 . − 4 5 x + 2 3 = 1 15 x = − 2 3 + 1 15 x = − 3 5