Tính nhanh: 270 x 20 + 58 x 270 + 28 x 270
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![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{-270}{x}+20=-70\)
\(⇔\dfrac{-270}{x}=-70-20\)
\(⇔x=\dfrac{-270}{-70-20}\)
\(⇔x=3\)
![](https://rs.olm.vn/images/avt/0.png?1311)
ĐKXĐ:\(x\ne0,x\ne-12\)
\(\dfrac{270}{x}-\dfrac{270}{x+12}=\dfrac{7}{10}\\ \Leftrightarrow270\left(\dfrac{1}{x}-\dfrac{1}{x+12}\right)=\dfrac{7}{10}\\ \Leftrightarrow\dfrac{x+12-x}{x\left(x+12\right)}=\dfrac{7}{2700}\\ \Leftrightarrow\dfrac{12}{x^2+12x}=\dfrac{7}{2700}\\ \Leftrightarrow7x^2+84x-32400=0\)
Xem lại đề
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a) 1 267 + 99 + 501 = 1 267 + (99 + 501)
= 1 267 + 600 = 1 867
25 x 14 x 4 = (25 x 4) x 14
= 100 x 14 = 1 400
b) 3 905 x (50 – 1) = 3 905 x 50 – 3 905 x 1
= 195 250 – 3 905 = 191 345
270 : ( 27 x 2 ) = 270 : 27 : 2
= 10 : 2 = 5
c) 115 x 58 + 115 x 42 = 115 x (58 + 42)
= 115 x 100 = 11 500
136 x 67 – 136 x 66 = 136 x (67 – 66)
= 136 x 1 = 136
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= (405 : 270 - 405 : 270) x 1234567890 + 2007
= 0 x 1234567890 + 2007
= 0 + 2007 = 2007
k mk nha
\(\left(40,5\div27-405\div270\right)\times1234567890+2007\)
\(=\text{ }\left[\left(40,5\times10\right)\div\left(27\times10\right)-405\div270\right]\times1234567890+2007\)
\(=\left(405\div270-405\div270\right)\times1234567890+2007\)
\(=0\times1234567890+2007\)
\(=0+2007\)
\(=2007\)
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Tính nhanh :
( x - 15 ) * 7 - 270 : 45 = 169
(x - 15) * 7 - 270 : 45 = 169
(x - 15) * 7 - 6 = 169 + 6
(x - 15) * 7 = 175
x - 15 = 175 : 7
x - 15 = 25
x = 25 + 15
x = 40
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 4 . x + 15 = - 5
⇒ 4 . x = - 5 – 15
⇒ 4 . x = - 20
⇒ x = - 20 : 4
⇒ x = - 5.
Vậy x = - 5.
b) (- 270) : x – 20 = 70.
⇒ (- 270) : x = 70 + 20
⇒ (- 270) : x = 90
⇒ x = (- 270) : 90
⇒ x = - 3
Vậy x = - 3
![](https://rs.olm.vn/images/avt/0.png?1311)
a) x - 140 : 35 = 270
x - 4 = 270
x = 270 + 4
x = 274
b) ( x-140) : 35 = 270
x-140 = 270 x 35
x-140 = 9 450
x = 9 450 + 140
x = 9 590
các phần cn lại lm tương tự nha bn!
![](https://rs.olm.vn/images/avt/0.png?1311)
Tìm x :
x + 1/3 = 4/5
x = 4/5 - 1/3
x = 12/15 - 5/15
x = 7/15
x - 1/2 = 2/7
x = 2/7 + 1/2
x = 4/14 + 7/14
x = 11/14
4/7 × x = 1/3
x = 1/3 : 4/7
x = 1/3 × 7/4
x = 7/12
x : 2/5 = 2/9
x = 2/9 × 2/5
x = 4/45
20 × 7 : ( 5 × x - 3 × 5 ) = 4
140 : 5 × ( x - 3 ) = 4
5 × ( x - 3 ) = 140 : 4
5 × ( x - 3 ) = 35
x - 3 = 35 : 5
x - 3 = 7
x = 7 + 3
x = 10
x - 270 = 420 : 105
x - 270 = 4
x = 4 + 270
x = 274
x - 140 : 35 = 270
x - 4 = 270
x = 270 + 4
x = 274
x + 1/3 = 4/5
x = 4/5 - 1/3
x = 7/15
x - 1/2 = 2/7
x = 2/7 + 1/2
x = 11/14
4/7 * x = 1/3
x = 1/3 : 4/7
x = 7/12
x : 2/5 = 2/9
x = 2/9 * 2/5
x 4 / 45
20 * 7 : ( 5*x - 3 * 5) =4
= 140 :(5*x -3 *5) =4
5*x- 3*5 = 140 : 4
5*x - 3 * 5 = 35
5* x = 35 + 3 * 5
5 * x = 50
x = 50 : 5
x = 10
x - 270 = 402 : 105
x - 270 = 4
x = 270 + 4
x = 274
x- 140 : 35 = 270
x - 4 = 270
x = 270 + 4
x = 274
270*20+58*270+28*270=270*/20+58+28\=270*100=270