X.3-13=4
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\(\dfrac{-4}{3}-\dfrac{5}{7}+\dfrac{4}{3}=\left(\dfrac{4}{3}+\dfrac{-4}{3}\right)-\dfrac{5}{7}=0-\dfrac{5}{7}=-\dfrac{5}{7}\)
\(\dfrac{3}{13}\cdot\dfrac{6}{11}+\dfrac{3}{13}\cdot\dfrac{9}{11}-\dfrac{3}{13}\cdot\dfrac{4}{11}=\dfrac{3}{13}\cdot\left(\dfrac{6}{11}+\dfrac{9}{11}-\dfrac{4}{11}\right)=\dfrac{3}{13}\cdot1=\dfrac{3}{13}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{13}{4}.\frac{2}{3}.\frac{4}{13}.\frac{3}{3}=\left(\frac{13}{4}.\frac{4}{13}\right).\left(\frac{2}{3}.\frac{3}{3}\right)=\frac{2}{3}.1=\frac{2}{3}\)
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\(\dfrac{-13}{4}.\dfrac{3}{7}-\dfrac{13}{4}.\dfrac{10}{7}-\dfrac{13}{7}\)
\(=\dfrac{13}{4}.\dfrac{-3}{7}-\dfrac{13}{4}.\dfrac{10}{7}-\dfrac{13}{7}\)
\(=\dfrac{13}{4}.\left(\dfrac{-3}{7}-\dfrac{10}{7}\right)-\dfrac{13}{7}\)
\(=\dfrac{13}{4}.\dfrac{-13}{7}-\dfrac{13}{7}\)
\(=\dfrac{-13}{4}.\dfrac{13}{7}-\dfrac{13}{7}\)
\(=\dfrac{13}{7}.\left(\dfrac{-13}{4}-1\right)\)
\(=\dfrac{13}{7}.-\dfrac{17}{4}\)
\(=-\dfrac{221}{28}\)
* Cách làm nhanh: Với biểu thức như trên, hai phân số nhân với nhau có thể đổi dấu cho nhau.*
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1.\(13.87+13.12+13\)
\(=13\left(87+12+1\right)\)
\(=13.100=1300\)
2.Đề sai à ???
3.\(x\left(x+4\right)-x\left(x-6\right)\)
\(=x^2+4x-x^2+6x\)
\(=10x\)
\(=10.123=1230\)
1, \(13.87+13.12+13=13\left(87+12+1\right)=13.100=1300\)
2, bổ sung \(\left(x-3\right)2x+\left(x-3\right)y=\left(x-3\right)\left(2x+y\right)\)
Thay x = 13 ; y = 4 ta được : \(\left(13-3\right)\left(26+4\right)=10.30=300\)
3, \(x\left(x+4\right)-x\left(x-6\right)=x\left(x+4-x+6\right)=10x\)
Thay x = 123 ta được \(1230\)
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a: =16-2+91=14+91=105
b: =9*5+8*10-27=45+53=98
c: =32+65-3*8=8+65=73
d; \(=5^3-10^2=125-100=25\)
e: \(=4^2-3^2+1=8\)
f: =9*16-16*8-8+16*4
=16(9-8+4)-8
=16*5-8
=72
a) \(2^4-50:25+13\cdot7\)
\(=2^4-2+91\)
\(=16-2+91\)
\(=14+91\)
\(=105\)
b) \(3^2\cdot5+2^3\cdot10-3^4:3\)
\(=9\cdot5+8\cdot10-3^3\)
\(=45+80-27\)
\(=98\)
c) \(2^5+5\cdot13-3\cdot2^3\)
\(=32+65-3\cdot8\)
\(=32+65-24\)
\(=73\)
d) \(5^{13}:5^{10}-5^2\cdot2^2\)
\(=5^{13-10}-\left(5\cdot2\right)^2\)
\(=5^3-10^2\)
\(=125-100\)
\(=25\)
e) \(4^5:4^3-3^9:3^7+5^0\)
\(=4^{5-3}-3^{9-7}+1\)
\(=4^2-3^2+1\)
\(=16-9+1\)
\(=8\)
f) \(3^2\cdot2^4-2^3\cdot4^2-2^3\cdot5^0+4^2\cdot2^2\)
\(=3^2\cdot4^2-2^3\cdot4^2-2^3\cdot1+4^2\cdot2^2\)
\(=4^2\cdot\left(3^2-2^3+2^2\right)-2^3\)
\(=4^2\cdot\left(9-8+4\right)-8\)
\(=16\cdot5-8\)
\(=72\)
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a) Thiếu đề
b) ` 4/7 xx 8/13 + 8/13 xx 3/7`
= ` 8/13 xx ( 4/7 + 3/7)`
` = 8/13 xx 7/7`
` = 8/13 xx 1`
` = 8/13`
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\(a.=\frac{4}{13}\times\frac{13}{4}\times\frac{2}{3}\times\frac{3}{2}\)
\(=1\times1\)
\(=1\)
\(b.=\frac{19}{13}+\frac{7}{13}+\frac{14}{6}+\frac{4}{6}+\frac{1}{9}+\frac{17}{9}\)
\(=\frac{26}{13}+\frac{18}{6}+\frac{18}{9}\)
\(=2+3+2\)
\(=7\)
4/13 * 2/3 * 13/4* 3/2= (4/13 * 13/4 )* (2/3 * 3*2) = 1*1=1
19/13 + 14/6 + 1/9 + 4/6 + 7/13 + 17/9 = (19/13 + 7/13) + (14/6 + 4/6) + (1/9 + 17/9) = 2 + 3 + 2 =7
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1) = \(\frac{3}{5}\)
2) =\(\frac{6}{7}\)
3)\(\frac{9}{13}\)
4)\(\frac{4}{13}\)
x.3 - 13 = 4
⇒ x.3 = 4 + 13
⇒ x.3 = 17
⇒ x = 17 : 3
⇒ x = \(\dfrac{17}{3}\)