\(\frac{12}{18}\).........?
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\(\frac{15-\frac{15}{7}-\frac{15}{12}-\frac{15}{98}}{18-\frac{18}{7}-\frac{18}{12}-\frac{18}{98}}\)= \(\frac{15-15\left(\frac{1}{7}+\frac{1}{12}+\frac{1}{98}\right)}{18-18\left(\frac{1}{7}+\frac{1}{12}+\frac{1}{98}\right)}\)=\(\frac{15\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)}{18\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)}\)= \(\frac{15}{18}\)=\(\frac{5}{6}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{15-\frac{15}{7}-\frac{15}{12}-\frac{15}{98}}{18-\frac{18}{7}-\frac{18}{12}-\frac{18}{98}}=\frac{15\left(1+\frac{1}{7}+\frac{1}{12}+\frac{1}{98}\right)}{18\left(1+\frac{1}{7}+\frac{1}{12}+\frac{1}{98}\right)}=\frac{15}{18}=\frac{5}{6}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
A=15x(1/7-1/12-1/98)/18(1/7-1/12-1/98)
A=15/18
A=5/6
h nhe!!!
\(A=\frac{15\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)}{18\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)}\)
\(A=\frac{15}{18}=\frac{5}{6}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=\frac{15\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)}{18\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{18}\right)}=\frac{15}{18}\)
\(A=\frac{15\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)}{18\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)}=\frac{15}{18}=\frac{5}{6}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
$\frac{4}{3} = \frac{{4 \times 6}}{{3 \times 6}} = \frac{{24}}{{18}}$
Vậy quy đồng mẫu số hai phân số $\frac{4}{3}$ và $\frac{{12}}{{18}}$, ta được các phân số $\frac{{24}}{{18}}$ và $\frac{{12}}{{18}}$
Vậy câu đúng là a; câu sai là b , c
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có:
A = [15 x (1-1/7-1/12-1/98)] / [ 18 x (1-1/7-1/12-1/98)]
= 15/18 = 5/6
\(A=\frac{15\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)}{18\left(1-\frac{1}{7}-\frac{1}{12}-\frac{1}{98}\right)}=\frac{15}{18}=\frac{15:3}{18:3}=\frac{5}{6}\)
k cho mk nha
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{12}{18}=\dfrac{24}{36}=\dfrac{72}{108}=\dfrac{12+24+72}{18+36+108}=\dfrac{12-24+72}{18-36+108}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,\frac{20^{12}\cdot6^{14}}{8^{13}\cdot15^{12}}\)
\(=\frac{5^{12}\cdot2^{24}\cdot2^{14}\cdot3^{14}}{2^{39}\cdot3^{12}\cdot5^{12}}\)
\(=\frac{5^{12}\cdot2^{38}\cdot3^{14}}{2^{39}\cdot3^{12}\cdot5^{12}}=\frac{3^2}{2}=\frac{9}{2}\)
\(b,\frac{45^{12}\cdot10^{14}}{18^{13}\cdot25^{12}}\)
\(=\frac{5^{12}\cdot3^{24}\cdot2^{14}\cdot5^{14}}{2^{13}\cdot3^{26}\cdot5^{24}}\)
\(=\frac{5^{26}\cdot3^{24}\cdot2^{14}}{2^{13}\cdot3^{26}\cdot5^{24}}=\frac{5^2\cdot2}{3^2}=\frac{50}{9}\)
\(c,\frac{18^{12}\cdot27^8}{6^8\cdot3^{40}}\)
\(=\frac{2^{12}\cdot3^{24}\cdot3^{24}}{2^8\cdot3^8\cdot3^{40}}\)
\(=\frac{2^{12}\cdot3^{48}}{2^8\cdot3^{48}}=2^4=16\)
\(d,\frac{12^{14}\cdot9^{18}}{8^9\cdot27^{17}}\)
\(=\frac{3^{14}\cdot2^{28}\cdot3^{36}}{2^{27}\cdot3^{51}}\)
\(=\frac{3^{50}\cdot2^{28}}{2^{27}\cdot3^{51}}=\frac{2}{3}\)
làm hơi tắt nên chịu khó hiểu
\(\frac{12}{18}=\frac{12:6}{18:6}=\frac{2}{3}.\)
TL :
\(\frac{2}{3}\)
HT
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