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a , 5.6 + 5.7 / 5.8 + 20 = 5.6 + 5.7 / 5.8 + 5 . 4 = 5 . ( 6+7 ) / 5 . ( 8 + 4 ) = 6 + 7 / 8 + 4 = 13 / 12 8 . 9 + 4 .15 / 12 . 7 - 180 = 4 . 2 . 3 . 3 + 2 . 2 . 3 . / 4 . 3 . 7 - 180 = 4 . 2 . 3 . 3 + 2.2.3.5 / 3 . 4 . 7 - 3 . 2 . 2 . 3. 5 = 1 . 2 . 1 . 1 + 1 . 1 . 1. 1 / 1 . 1 . 7 - 1 . 1 . 1 . 1 .1 = 3 / 6 = 1/2 b , 2^5 . 7 +2^5 / 2^5 . 5^2 - 2^5 .3 = 2^5 . ( 7 + 1) / 2^5 ( 5^2 - 3 ) = 7+1 / 5^2 - 3 = 8 / 22 = 4 / 11 3^4 . 5 - 3^6 / 3^4 . 13 + 3^4 = 3^4 . 5 - 3^4 . 3^2 / 3^4 . 13 + 3^4 = 3^4 . ( 5 - 3^2 ) / 3^4 . ( 13 + 1 ) = 5 - 3^2 / 13 + 1 = -4 / 14 = -2 / 12
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Ta có: \(\frac{2^5.7+2^5}{2^5.5^2-2^5.3}\) = \(\frac{2^5.\left(7+1\right)}{2^5.\left(5^2-3\right)}\) = \(\frac{2^5.8}{2^5.22}\) = \(\frac{8}{22}\) =\(\frac{56}{154}\)
\(\frac{3^4.5-3^6}{3^4.13+3^4}\) = \(\frac{3^4.\left(5-3^2\right)}{3^4.\left(13+1\right)}\) = \(\frac{3^4.\left(-4\right)}{3^4.14}\) = \(\frac{-4}{14}\)= \(\frac{-44}{154}\)
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a: \(\dfrac{25\cdot9-25\cdot17}{-8\cdot80-8\cdot10}=\dfrac{25\cdot\left(-8\right)}{\left(-8\right)\cdot\left(80+10\right)}=\dfrac{25}{90}=\dfrac{5}{18}=\dfrac{250}{900}\)
\(\dfrac{48\cdot12-48\cdot15}{\left(-3\right)\cdot\left(270+30\right)}=\dfrac{48}{300}=\dfrac{8}{50}=\dfrac{144}{900}\)
\(\dfrac{2^5\cdot3}{600}=\dfrac{96}{600}=\dfrac{144}{900}\)
b: \(\dfrac{2^5\cdot7+25}{25\cdot5^2-2^5\cdot3}=\dfrac{32\cdot7+25}{25\cdot25-32\cdot3}=\dfrac{249}{529}=\dfrac{1743}{7\cdot529}\)
\(\dfrac{3^4\cdot5-3^6}{3^4\cdot13+3^4}=\dfrac{3^4\left(5-9\right)}{3^4\left(13+1\right)}=\dfrac{-4}{14}=\dfrac{-2}{7}=\dfrac{-1058}{7\cdot529}\)
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Đáp án cần chọn là: A
3 . 4 − 3 . 7 6 . 5 + 9 = 12 − 21 30 + 9 = − 9 39 = − 3 13 3 . 4 − 3 . 7 6 . 5 + 9 = 12 − 21 30 + 9 = − 9 39 = − 3 13 6 . 9 − 2 . 17 63 . 3 − 119 = 54 − 34 189 − 119 = 20 70 = 2 7
MSC = 91
− 3 13 = − 3.7 13.7 = − 21 91 ; 2 7 = 2.13 7.13 = 26 91
Vậy sau khi quy đồng ta được hai phân số − 21 91 và 26 91
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\frac{25.9-25.17}{-8.80-8.10}=\frac{25.\left(9-17\right)}{-8.\left(80+10\right)}=\frac{25.\left(-8\right)}{-8.90}=\frac{5}{18}\)
b) \(\frac{48.12-48.15}{-3.270-3.30}=\frac{48.\left(12-15\right)}{-3.\left(270+30\right)}=\frac{48.\left(-3\right)}{-3.300}=\frac{4}{25}\)
c) \(\frac{2^5.7+2^5}{2^5.5^2-2^5.3}=\frac{2^5.\left(7+1\right)}{2^5.\left(5^2-3\right)}=\frac{2^5.8}{2^5.\left(25-3\right)}=\frac{2^5.8}{2^5.22}=\frac{4}{11}\)
d) \(\frac{3^4.5-3^6}{3^4.13+3^4}=\frac{3^4.\left(5-3^2\right)}{3^4.\left(13+1\right)}=\frac{3^4.\left(5-9\right)}{3^4.14}=\frac{3^4.\left(-4\right)}{3^4.14}=\frac{-2}{7}\)
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\(a,\frac{5\cdot6+5\cdot7}{5\cdot8+20}=\frac{\left(5\cdot6+5\cdot7\right)\div2}{\left(5.8+20\right)\div2}=\frac{13}{12}\)
\(\frac{8.9-4.15}{12.7-180}=\frac{12.6-12.5}{12.7-12.15}=\frac{1}{-8}=\frac{-1}{8}\)
\(Ta\)\(co\)\(\frac{13}{12}=\frac{13.2}{12.2}=\frac{26}{24}\)
\(\frac{-1}{8}=\frac{3\left(-1\right)}{3.8}=\frac{-3}{24}\)
Phần b bạn tính ra rồi làm tương tự phần a nha chúc bạn học giỏi!!!
Xét: 2^5x7+2^5/2^5.5^2-2^5.3
=2^5x7+2^5x1/2^5x25-2^5x3
=2^5x(7+1)/2^5x(25-3)
=2^5x8/2^5x22
=8/22
=4/11
Xét: 3^4x5-3^6/3^4x13+3^4
=3^4x5-3^4x3^2/3^4x13+3^4
=3^4x(5-9)/3^4x(13+1)
=3^4x(-4)/3^4x14
=-4/14
=-2/7
Mẫu số chung của 4/11 và -2/7 là 77
-->Thừa số phụ tương ứng là 7 và 11
Quy đồng : 4/11=4x7/11x7=28/77
-2/11=(-2)x11/7x11=-22/77
Vậy ta có 28/77 và -22/77