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1)\(x=\left(\dfrac{1}{5}+\dfrac{2}{3}\right):\dfrac{4}{7}=\left(\dfrac{3}{15}+\dfrac{10}{15}\right):\dfrac{4}{7}=\dfrac{13}{15}:\dfrac{4}{7}=\dfrac{91}{60}\)
2)\(x=\left(-\dfrac{3}{10}-\dfrac{3}{4}\right):\dfrac{1}{2}=\left(-\dfrac{6}{20}-\dfrac{15}{20}\right):\dfrac{1}{2}=-\dfrac{21}{20}:\dfrac{1}{2}=-\dfrac{21}{10}\)
3)\(x=-\dfrac{24}{36}-\dfrac{7}{15}=-\dfrac{2}{3}-\dfrac{7}{15}=\dfrac{-10}{15}-\dfrac{7}{15}=-\dfrac{17}{15}\)
1) \(\dfrac{4}{7}x=\dfrac{1}{5}+\dfrac{2}{3}\)
\(\dfrac{4}{7}x=\dfrac{13}{15}\)
\(x=\dfrac{91}{60}\)
2) \(\dfrac{1}{2}x=-\dfrac{3}{10}-\dfrac{3}{4}\)
\(\dfrac{1}{2}x=-\dfrac{21}{20}\)
\(x=-\dfrac{21}{10}\)
3) \(x=-\dfrac{24}{36}-\dfrac{7}{15}\)
\(x=\dfrac{-2}{3}+\dfrac{7}{15}\)
\(x=-\dfrac{17}{15}\)
\(500-\left\{5\left[409-\left(2^3\cdot3-21\right)^2+10^3\right]\right\}:15\)
\(=500-\left\{5\left[409-9+1000\right]\right\}:15\)
\(=500-\left\{5\cdot1400\right\}:15\)
\(=500-7000:15\)
\(=500-\dfrac{1400}{3}\)
\(=\dfrac{100}{3}\)
\(67-\left[8+7\cdot3^2-24:6+\left(9-7\right)^2\right]:15\)
\(=67-\left[8+7\cdot9-24:6+4\right]:15\)
\(=67-\left[8+63-4+4\right]:15\)
\(=67-71:15\)
\(=67-\dfrac{71}{15}\)
\(=\dfrac{934}{15}\)
\(PeaGea\)
1)
a) 2x + 5 = 3⁴ : 3²
2x + 5 = 3²
2x + 5 = 9
2x = 9 - 5
2x = 4
x = 4 : 2
x = 2
b) (3x - 24).73 = 2.74
(3x - 24).73 = 148
3x - 24 = 148/73
3x = 148/73 + 24
3x = 1900/73
x = 1900/73 : 3
x = 1900/219
c) [3.(42 - x)] + 15 = 23.3
126 - 3x + 15 = 69
141 - 3x = 69
3x = 141 - 69
3x = 72
x = 72 : 3
x = 24
d) 126 + (132 - x) = 300
132 - x = 300 - 126
132 - x = 174
x = 132 - 174
x = -42
2)
a) 120 - (x + 55) = 60
x + 55 = 120 - 60
x + 155 = 60
x = 60 - 55
x = 5
b) (7x - 11).3 = 25.52 + 200
(7x - 11).3 = 1500
7x - 11 = 1500 : 3
7x - 11 = 500
7x = 500 + 11
7x = 511
x = 511 : 7
x = 73
c) 2x + 2x + 4 = 544
4x = 544 - 4
4x = 540
x = 540 : 4
x = 135
Ta có:8=23
10=2.5
24=24.5
BCNN(...)=23.5=24.5=40
b)Ta có:
16=24
24=23.3
BCNN(...)=24.3=48
c)Ta có:
60=22.3.5
140=22.5.7
BCNN(...)=22.3.5.7=420
Mấy bài sau bn cứ lm như thế này nhé^^
\(3A=3+3^2+3^3+...+3^{21}\\ 2A=3^{21}-1\\ A=\dfrac{3^{21}-1}{2}\\ 5B=5^2+5^3+...+5^{11}\\ 4B=5^{11}-5\\ B=\dfrac{5^{11}-5}{4}\\ 2C=2^5+2^6+...+2^{31}\\ C=2^{31}-2^4\)
a) 8 = 2³
10 = 2.5
20 = 2².5
BCNN(8; 10; 20) = 2³.5 = 40
b) 16 = 2⁴
24 = 2³.3
BCNN(16; 24) = 2⁴.3 = 48
c) 60 = 2².3.5
140 = 2².5.7
BCNN(60; 140) = 2².3.5.7 = 420
d) 8 = 2³
9 = 3²
11 = 11
BCNN(8; 9; 11) = 2³.3².11 = 792
e) 24 = 2³.3
40 = 2³.5
162 = 2.3⁴
BCNN(24; 40; 162) = 2³.3⁴.5 = 3240
f) 56 = 2³.7
70 = 2.5.7
126 = 2.3².7
BCNN(56; 70; 126) = 2³.3².5.7 = 2520
g) 28 = 2².7
20 = 2².5
30 = 2.3.5
BCNN(28; 20; 30) = 2².3.5.7 = 420
h) 34 = 2.17
32 = 2⁵
20 = 2².5
BCNN(34; 32; 20) = 2⁵.5.17 = 2720
k) 42 = 2.3.7
70 = 2.5.7
20 = 2².5
BCNN(42; 70; 20) = 2².3.5.7 = 420
l) 9 = 3²
10 = 2.5
11 = 11
BCNN(9; 10; 11) = 2.3².5.11 = 990
`3^{2}.[(5^{2}-3):11]-2^{4}+2.10^{3}`
`=9.[(25-3):11]-16+2.1000`
`=9.(22:11)-16+2000`
`=9.2-16+2000`
`=2002`
=9.[(25-3):11]-16+2.1000
=9.[22:11]-16+2.1000
=9.2-16+2.1000
=18-16+2000
=2+2000
=2002