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Bài 14 :
a. 55/66 = 55 : 11/66 : 11 = 5/6 b. -33/88 = -33 : 11/88 : 11 = -3/8 c. 2020/8080 = 2020 : 2020/8080 : 2020 = 1/4
d. 2121/-4242 = 2121 : (-101)/(-4242) : (-101) = 21/42 = 1/2
e. 130130/-260260 = 130130 : (-1001)/(-260260) : ( -1001 ) = -130/260 = -1/2
f. 1616/-1313 = 1616 : (-101)/(-1313) : (-101 ) = -16/13
Chúc bạn học tốt nha !
Bài 14 khá đơn giản nên mình sẽ bỏ qua, bạn tự làm đc mà xD
15. a) \(\frac{13\cdot9-13\cdot2}{25-12}=\frac{13\left(9-2\right)̸}{13}=7\)
b) \(\frac{42-14\cdot8}{7+21\cdot3}=\frac{14\cdot3-14\cdot8}{7+63}=\frac{14\left(3-8\right)}{70}=\frac{14\cdot\left(-5\right)}{70}=\frac{-70}{70}=-1\)
c) \(\frac{9\cdot6-18\cdot4}{12\cdot3}=\frac{\left(9\cdot2\right)\cdot\left(6:2\right)-18\cdot4}{36}=\frac{18\cdot3-18\cdot4}{36}=\frac{18\left(3-4\right)}{36}=\frac{-18}{36}=\frac{-1}{2}\)
d) \(\frac{5\cdot5^2}{9\cdot10^2-4\cdot10^2}=\frac{5\cdot5^2}{10^2\left(9-4\right)}=\frac{5\cdot5^2}{10^2\cdot5}=\frac{1}{2^2}=\frac{1}{4}\)
e) \(\frac{\left(-7\right)\cdot3-4\cdot\left(-6\right)}{\left(-5\right)\cdot3-2\cdot3}=\frac{-21+24}{-15-6}=\frac{3}{-21}=\frac{-1}{7}\)
f) \(\frac{\left(-17\right)\cdot13+17\cdot2}{-11\cdot2-11\cdot19}=\frac{-\left[17\cdot\left(13+2\right)\right]}{-\left[11\cdot\left(2-19\right)\right]}=\frac{-17\cdot13-\left(-17\right)\cdot2}{-11\cdot2+\left(-11\right)\cdot19}=\frac{-17\left(13-2\right)}{-11\left(2+19\right)}=\frac{-17\cdot11}{-11\cdot19}=\frac{-17}{-19}=\frac{17}{19}\)
* Hơi dài xD , mong bạn thông cảm *
a) \(\dfrac{11\cdot8-11\cdot3}{17-6}\)
\(=\dfrac{11\cdot\left(8-3\right)}{11}=5\)
b) \(\dfrac{24-12\cdot13}{12+4\cdot9}\)
\(=\dfrac{12\cdot\left(2-13\right)}{12\left(1+3\right)}=\dfrac{-11}{4}\)
a) \(\dfrac{22}{55}=\dfrac{2}{5}\)
b) \(\dfrac{-63}{81}=\dfrac{-7}{9}\)
c) \(\dfrac{2.14}{7.8}=\dfrac{2.7.2}{7.2.2.2}=\dfrac{1}{2}\)
d) \(\dfrac{49+7.49}{49}=\dfrac{49.\left(7+1\right)}{49}=\dfrac{49.8}{49}=8\)
a: \(=\dfrac{-4\cdot13\cdot9\cdot5}{3\cdot4\cdot5\cdot2\cdot13}=\dfrac{3}{2}\)
b: \(=\dfrac{1}{2}\cdot\dfrac{1}{3}\cdot5=\dfrac{5}{6}\)
\(\dfrac{4\cdot5\cdot36}{35\cdot9\cdot2}=\dfrac{2^2\cdot5\cdot2^2\cdot3^2}{5\cdot7\cdot3^2\cdot2}=\dfrac{2^3}{7}=\dfrac{8}{7}\left(C\right)\)
Tính các tổng dưới đây sau khi đã rút gọn phân số :
a)\(\dfrac{7}{21}\) + \(\dfrac{9}{-36}\) = \(\dfrac{7}{21}\)+\(\dfrac{-9}{36}\)=\(\dfrac{1}{3}\)+\(\dfrac{-1}{4}\)=\(\dfrac{4}{12}\)+\(\dfrac{-3}{12}\)=\(\dfrac{1}{12}\)
b) \(\dfrac{-12}{18}\)+\(\dfrac{-21}{35}\)=\(\dfrac{-2}{3}\)+\(\dfrac{-3}{5}\)=\(\dfrac{-10}{15}\)+\(\dfrac{-9}{15}\)=\(\dfrac{-19}{15}\)
c) \(\dfrac{-3}{21}\)+\(\dfrac{6}{42}\)=\(\dfrac{-1}{7}\)+\(\dfrac{1}{7}\)=0
d) \(\dfrac{-18}{24}\)+\(\dfrac{15}{-21}\)=\(\dfrac{-18}{24}\)+\(\dfrac{-15}{21}\)=\(\dfrac{-3}{4}\)+\(\dfrac{-5}{7}\)=\(\dfrac{-21}{28}\)+\(\dfrac{-20}{28}\)=\(\dfrac{-41}{28}\)
a) \(=\dfrac{-5}{12}.\dfrac{2}{7}+\dfrac{7}{12}.-\dfrac{3}{14}\)
\(=-\dfrac{5}{42}-\dfrac{1}{8}\)
= \(-\dfrac{41}{168}\)
b) \(=\dfrac{2.\left(-13\right).9.10}{\left(-3\right).4.\left(-5\right).26}\)
\(=\dfrac{1.1.3.\left(-2\right)}{\left(-1\right).2.1.\left(-2\right)}=\dfrac{3}{\left(-1\right).2}\)
\(=-\dfrac{3}{2}\)
a: \(=\dfrac{13\cdot\left(9-2\right)}{13}=7\)
b: \(=\dfrac{14\left(3-8\right)}{7\left(1+3\cdot3\right)}=2\cdot\dfrac{-5}{10}=-1\)
c: \(=\dfrac{54-72}{36}=\dfrac{-18}{36}=-\dfrac{1}{2}\)
d: \(=\dfrac{5^3}{10^2\cdot5}=\dfrac{5^2}{100}=\dfrac{1}{4}\)