-x + 21 = 15 + 2x Giúp mình với
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Ta có :
- x + 21 = 15 + 2x
=> 21 - 15 = 2x + x
=> 6 = 3x
=> x = 2
Vậy x = 2
-x+21=15+2x
=> -x-2x=15-21
=> -3x=-6
=> x=2
=14/15*20/21*...*209/210
\(=\dfrac{4\cdot7}{5\cdot6}\cdot\dfrac{5\cdot8}{6\cdot7}\cdot...\cdot\dfrac{19\cdot22}{20\cdot21}\)
\(=\dfrac{4\cdot5\cdot6\cdot...\cdot19}{5\cdot6\cdot7\cdot...\cdot20}\cdot\dfrac{7\cdot8\cdot9\cdot...\cdot22}{6\cdot7\cdot8\cdot...\cdot21}=\dfrac{11}{15}\)
\(A=2\dfrac{3}{13}\times\dfrac{13}{58}\times8\times2\dfrac{15}{24}\times\dfrac{8}{21}\)
\(A=\dfrac{29}{13}\times\dfrac{13}{58}\times8\times\dfrac{21}{8}\times\dfrac{8}{21}\)
\(A=\dfrac{29\times13\times8\times21\times8}{13\times58\times8\times21}\)
\(A=\dfrac{1\times1\times1\times1\times8}{1\times2\times1\times1}\)
\(A=\dfrac{8}{2}\)
\(A=4\)
\(A=\dfrac{29}{13}\cdot\dfrac{13}{58}\cdot8\cdot\dfrac{21}{8}\cdot\dfrac{8}{21}=\dfrac{1}{2}\cdot8=4\)
1) 42/35 - [ 33/14 . 21/22 - ( 54/25 : 27/25 - 7/10 )]
= 42/35 - ( 9/4-13/10)
=42/35-19/20
=1/4
2) a) 5/21 . x/34 = 35/102
x/34=35/102 : 5/21
x/34=49/34
=> x=34
Vậy x=34
b) 15/x . 21/13 = 45/91
15/x=45/91 : 21/13
15/x=15/49
=> x=49
Vậy x=49
-x+21=15+2x
-x-2x=15-21
-3x=-6
x=2
-x+21=15+2x
-x-2x=15-21
-3x=-6
x=2