2×|15-x|=1/10×5/3
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3 x 15 + 21 x 15 + 85 x 5
= 45 + 315 + 425
= 785
15 - 30 + 40
= 25
21 + 19 - 50 + 10
= 0
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=-\dfrac{1}{20}+2\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{12}\times\dfrac{3}{12}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=-\dfrac{9}{20}\)
\(3\times15+21\times15+85\times5\\ =15\times\left(3+21\right)+425\\ =15\times24+425\\ =360+425\\ =785\)
\(15-30+40\\ =\left(15+40\right)-30\\ =55-30\\ =25\)
\(21+19-50+10\\ =\left(21+19\right)-\left(50-10\right)\\ =40-40\\ =0\)
\(\dfrac{1}{5}-\dfrac{1}{4}+2\)
\(=\dfrac{4}{20}-\dfrac{5}{20}+\dfrac{40}{20}\)
\(=\dfrac{\left(4+40\right)}{20}-\dfrac{5}{20}\)
\(=\dfrac{44}{20}-\dfrac{5}{20}\)
\(=\dfrac{39}{20}\)
\(\left(\dfrac{1}{4}+\dfrac{1}{6}\right)\times\left(\dfrac{1}{2}-\dfrac{1}{4}\right)\)
\(=\dfrac{5}{12}\times\dfrac{1}{4}\)
\(=\dfrac{5}{48}\)
\(\dfrac{1}{10}+\dfrac{1}{5}-\dfrac{3}{4}\)
\(=\dfrac{2}{20}+\dfrac{4}{20}-\dfrac{15}{20}\)
\(=\dfrac{6}{20}-\dfrac{15}{20}\)
\(=-\dfrac{9}{20}\)
a, (\(\dfrac{9}{10}\) - \(\dfrac{15}{16}\)) \(\times\) ( \(\dfrac{5}{12}\) - \(\dfrac{11}{15}\) - \(\dfrac{7}{20}\))
= (\(\dfrac{72}{80}\) - \(\dfrac{75}{80}\)) \(\times\) (\(\)\(\dfrac{25}{60}\) - \(\dfrac{44}{60}\) - \(\dfrac{21}{60}\))
= - \(\dfrac{3}{80}\) \(\times\) (- \(\dfrac{2}{3}\))
= \(\dfrac{1}{40}\)
b, (-1)3 + (- \(\dfrac{2}{3}\))2 : 2\(\dfrac{2}{3}\) + \(\dfrac{5}{6}\)
= -13 + \(\dfrac{4}{9}\) : \(\dfrac{8}{3}\) + \(\dfrac{5}{6}\)
= -1 + \(\dfrac{4}{9}\) \(\times\) \(\dfrac{3}{8}\) + \(\dfrac{5}{6}\)
= -1 + \(\dfrac{1}{6}\) + \(\dfrac{5}{6}\)
= -1 + 1
= 0
a, 48.84
= (22)8.(23)4
= 216.212
= 228
b, 415.515
= (4.5)15
= 2015
c, 210.15 + 210.85
= 210.(15 + 85)
= 210.100
=210.(2.5)2
= 212.52
d, 33.92
= 33 . (32)2
= 33.34
= 37
e, 512.7 - 511.10
= 511.(5.7 - 10)
= 511.25
=511.52
=513
f, \(x^1\).\(x^2\).\(x^3\)....\(x^{100}\)
= \(x^{1+2+3+...+100}\)
= \(x^{\left(1+100\right).100:2}\)
= \(x^{5050}\)
a: =>7/9:x=1/18-2/9=1/18-4/18=-3/18=-1/6
=>x=-7/9:1/6=-7/9*6=-42/9=-14/3
b: =>x*7/5=2/15+2/5=8/15
=>x=8/15:7/5=8/21
c: =>x-1/2=3/14:4/7=3/8
=>x=3/8+4/8=7/8
d: =>0,4x+0,3x-0,2x=0,7
=>0,5x=0,7
=>x=1,4
1) 2(x + 5) + 3(x + 7) = 41
2x + 10 + 3x + 21 = 41
5x + 31 = 41
5x = 10
x = 2
6) 7(x - 1) + 5(3 - x) = 11x - 10
7x - 7 + 15 - 5x = 11x - 10
2x + 8 = 11x - 10
-9x = -18
x = 2
2) 5(x + 6) + 2(x - 3) = 38
5x + 30 + 2x - 6 = 38
7x + 24 = 38
7x = 14
x = 2
7) 4(2 + x) + 3(x - 2) = 12
8 + 4x + 3x - 6 = 12
7x + 2 = 12
7x = 10
x = 10/7
3) 7(5 + x) + 2(x - 10) = 15
35 + 7x + 2x - 20 = 15
9x + 15 = 15
9x = 0
x = 0
8) 5(2 + x) + 4(3 - x) = 10x - 15
10 + 5x + 12 - 4x = 10x - 15
x + 22 = 10x - 15
9x = 37
x = 37/9
4) 3(x + 4) + (8 - 2x) = 22
3x + 12 + 8 - 2x = 22
x + 20 = 22
x = 2
9) 7(x - 2) + 5(3 - x) = 11x - 6
7x - 14 + 15 - 5x = 11x - 6
2x + 1 = 11x - 6
-9x = -7
x = 7/9
5) 4(x + 5) + 3(7 - x) = 49
4x + 20 + 21 - 3x = 49
x + 41 = 49
x = 8
10) 5(3 - x) + 5(x + 4) = 6 + 4x
15 - 5x + 5x + 20 = 6 + 4x
35 = 6 + 4x
4x = 29
x = 29/4
1) 2(x + 5) + 3(x + 7) = 41
2x + 10 + 3x + 21 = 41
5x + 31 = 41
5x = 41 - 31
5x = 10
x = 10 : 5
x = 2
2) 5(x + 6) + 2(x - 3) = 38
5x + 30 + 2x - 6 = 38
7x + 24 = 38
7x = 38 - 24
7x = 14
x = 14 : 7
x = 2
3) 7(5 + x) + 2(x - 10) = 15
35 + 7x + 2x - 20 = 15
9x + 15 = 15
9x = 15 - 15
9x = 0
x = 0
4) 3(x + 4) + (8 - 2x) = 22
3x + 12 + 8 - 2x = 22
x + 20 = 22
x = 22 - 20
x = 2
5) 4(x + 5) + 3(7 - x) = 49
4x + 20 + 21 - 3x = 49
x + 41 = 49
x = 49 - 41
x = 8
6) 7(x - 1) + 5(3 - x) = 11x - 10
7x - 7 + 15 - 5x = 11x - 10
2x - 11x + 8 = -10
-9x = -10 - 8
-9x = -18
x = -18 : (-9)
x = 2
7) 4(2 + x) + 3(x - 2) = 12
8 + 4x + 3x - 6 = 12
7x + 2 = 12
7x = 12 - 2
7x = 10
x = 10/7
8) 5(2 + x) + 4(3 - x) = 10x - 15
10 + 5x + 12 - 4x = 10x - 15
10x - 15 = x + 22
10x - x = 22 + 15
9x = 37
x = 37/9
9) 7(x - 2) + 5(3 - x) = 11x - 6
7x - 14 + 15 - 5x = 11x - 6
11x - 6 = 2x + 1
11x - 2x = 1 + 6
9x = 7
x = 7/9
10) 5(3 - x) + 5(x + 4) = 6 + 4x
15 - 5x + 5x + 20 = 6 + 4x
6 + 4x = 35
4x = 35 - 6
4x = 29
x = 29/4
a) x + 3/5 = -1/15
=> x = -1/15 - 3/5
=> x = -2/3
b) x/14 = 1/7 - 3/14
=> x/14 = -1/14
=> x = -1
c) -1/2x + 1/5 = 3/10
=> -1/2x = 3/10 - 1/5
=> -1/2x = 1/5
=> x = 1/5 : (-1/2)
=> x = -2/5
d) 4/5 - (2/15 + x) = 1/15
=> 4/5 - 2/15 - x = 1/15
=> 2/3 - x = 1/15
=> x = 2/3 - 1/15
=> x = 3/5
a) x* 1/5 - x* 2 * 2/15 = 4
x * 1/5 - x * 2 = 4 : 2/15
x * 15 - x * 2 = 30
x * ( 15 - 2 ) = 30
x * 13 = 30
x = 30 : 13
x = 30/13
b) ( x + x * 2 ) - 3 : 1/2 = 8
( x * 1 + x * 2 ) - 3 = 8 x 1/2
( x * 1 + x * 2 ) - 3 = 4
x * 1 + x * 2 = 4 + 3
x * 1 + x * 2 = 7
x * ( 1 + 2 ) = 7
x * 3 = 7
x = 7 : 3
x = 7/3
c)5 +( x * 1/2 - 4 ) = 15
x * 1/2 - 4 = 15 - 5
x * 1/2 - 4 = 10
x * 1/2 = 10 + 4
x * 1/2 = 14
x = 14 : 1/2
x = 7
a)x*1/5-x*2*2/15=4
x*1/5-x*4/15=4
x*1/5-4/15=4
x*(-1/15)=4
x=4:-1/15
x=-60
\(2.|15-x|=\frac{1}{10}.\frac{5}{3}\)
\(< =>|15-x|=\frac{1}{6}:2=\frac{1}{12}\)
\(< =>\orbr{\begin{cases}15-x=\frac{1}{12}\\15-x=-\frac{1}{12}\end{cases}}\)
\(< =>\orbr{\begin{cases}-x=\frac{1}{12}-15=-\frac{179}{12}\\-x=-\frac{1}{12}-15=-\frac{181}{12}\end{cases}}\)
\(< =>\orbr{\begin{cases}x=\frac{179}{12}\\x=\frac{181}{12}\end{cases}}\)
Bài làm:
Ta có: \(2.\left|15-x\right|=\frac{1}{10}.\frac{5}{3}\)
\(\Leftrightarrow\left|15-x\right|=\frac{1}{12}\)
\(\Leftrightarrow\orbr{\begin{cases}15-x=\frac{1}{12}\\15-x=-\frac{1}{12}\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=\frac{179}{12}\\x=\frac{181}{12}\end{cases}}\)
Vậy \(\orbr{\begin{cases}x=\frac{179}{12}\\x=\frac{181}{12}\end{cases}}\)