Rút gọn các phân số sau:
- 63 81
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\(\dfrac{18}{45}=\dfrac{2}{5}\dfrac{63}{81}=\dfrac{7}{9}\) minh chi co the lam the nay thoi vi minh dang co viec gap
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) \(\dfrac{49+7.49}{49}=\dfrac{49.\left(7+1\right)}{49}=\dfrac{49.8}{49}=8\)
rút gọn các phân số
a) 22/55 = 2/5
b) -63/81 = -7/9
\(a,\dfrac{52}{32}=\dfrac{13}{8}\\ \dfrac{55}{65}=\dfrac{11}{13}\\ MSC:104\\ =>\dfrac{13}{8}=\dfrac{13.13}{8.13}=\dfrac{169}{104}\\ \dfrac{11}{13}=\dfrac{11.8}{13.8}=\dfrac{88}{104}\)
\(b,\dfrac{72}{64}=\dfrac{9}{8}\\ \dfrac{54}{81}=\dfrac{2}{3}\\ MSC:24\\ \dfrac{9}{8}=\dfrac{9.3}{8.3}=\dfrac{27}{24}\\ \dfrac{2}{3}=\dfrac{2.8}{3.8}=\dfrac{16}{24}\\ c,\dfrac{24}{36}=\dfrac{2}{3}\\ \dfrac{12}{30}=\dfrac{2}{5}\\ MSC:15\\ \dfrac{2}{3}=\dfrac{2.5}{3.5}=\dfrac{10}{15}\\ \dfrac{2}{5}=\dfrac{2.3}{3.5}=\dfrac{6}{15}\)
\(d,\dfrac{80}{40}=2\\ \dfrac{45}{63}=\dfrac{5}{7}\\ MSC:7\\ 2=\dfrac{14}{7}\\ e,\dfrac{150}{50}=3\\ \dfrac{100}{200}=\dfrac{1}{2}\\ MSC:2\\ 3=\dfrac{6}{2}\\ f,\dfrac{54}{81}=\dfrac{2}{3}\\ \dfrac{69}{93}=\dfrac{23}{21}\\ MSC:21\\ \dfrac{2}{3}=\dfrac{2.7}{3.7}=\dfrac{14}{21}\)
\(a.\dfrac{52}{32}\text{=}\dfrac{13}{8};\dfrac{55}{65}\text{=}\dfrac{11}{13}\)
\(\dfrac{13.13}{13.8}\text{=}\dfrac{169}{104};\dfrac{11.8}{13.8}\text{=}\dfrac{88}{104}\)
\(c.\dfrac{24}{36}\text{=}\dfrac{2}{3};\dfrac{12}{30}\text{=}\dfrac{2}{5}\)
\(\dfrac{2.5}{3.5}\text{=}\dfrac{10}{15};\dfrac{2.3}{5.3}\text{=}\dfrac{6}{15}\)
\(b.\dfrac{72}{64}\text{=}\dfrac{9.3}{8.3}\text{=}\dfrac{27}{24};\dfrac{54}{81}\text{=}\dfrac{2.8}{3.8}\text{=}\dfrac{16}{24}\)
\(d.\dfrac{80}{40}\text{=}\dfrac{2.63}{63}\text{=}\dfrac{126}{63};\dfrac{45}{63}\)
\(e.\dfrac{150}{50}\text{=}\dfrac{3.2}{2}\text{=}\dfrac{6}{2};\dfrac{100}{200}\text{=}\dfrac{1}{2}\)
\(f.\dfrac{54}{81}\text{=}\dfrac{2.31}{3.31}\text{=}\dfrac{62}{93};\dfrac{69}{93}\)
\(\dfrac{75}{100}=\dfrac{3}{4};\dfrac{63}{126}=\dfrac{1}{2}\\ \dfrac{36}{27}=1\dfrac{1}{3};\dfrac{81}{54}=1\dfrac{1}{2};\dfrac{105}{405}=\dfrac{7}{27}\)
\(\dfrac{24}{32}=\dfrac{24:8}{32:8}=\dfrac{3}{4}\)
\(\dfrac{75}{100}=\dfrac{75:25}{100:25}=\dfrac{3}{4}\)
\(\dfrac{45}{60}=\dfrac{45:15}{60:15}=\dfrac{3}{4}\)
\(\dfrac{27}{63}=\dfrac{27:9}{63:9}=\dfrac{3}{7}\)
\(\dfrac{24}{32}=\dfrac{24:8}{32:8}=\dfrac{3}{4}\)
\(\dfrac{45}{6}=\dfrac{45:3}{6:3}=\dfrac{15}{2}\)
\(\dfrac{75}{100}=\dfrac{75:25}{100:25}=\dfrac{3}{4}\)
\(\dfrac{27}{63}=\dfrac{27:9}{63:9}=\dfrac{3}{7}\)
1) Các phân số tối giản là: \(\frac{1}{5};\frac{5}{7};\frac{-2}{9}\)
2) a) \(\frac{28}{36}=\frac{28:4}{36:4}=\frac{7}{9}\)
b) \(\frac{-63}{90}=\frac{-63:9}{90:9}=\frac{-7}{10}\)
c) \(\frac{40}{-120}=\frac{40:40}{-120:40}=\frac{-1}{3}\)
3) a) \(\frac{2.4}{6.18}=\frac{2.2.2}{2.3.3.2.3}=\frac{2}{27}\)
b) \(\frac{3.5.7}{6.9.14}=\frac{3.5.7}{2.3.9.2.7}=\frac{5}{36}\)
c) \(\frac{4.7-4.5}{64}=\frac{4.\left(7-5\right)}{64}=\frac{4.2}{64}=\frac{8}{64}=\frac{1}{8}\)
4) Muốn rút gọn một phân số chưa tối giản, ta tìm ƯCLN của cả hai số ở tử và mẫu, rồi cùng đem cả tử và mẫu chia cho số chung vừa tìm được.
Hướng dẫn: Chia cả tử và mẫu cho UCLN của chúng:
ƯCLN(-63, 81) = 9. Do đó: