b 12 và 52
c) 36 và 990
d) 54 và 36
e) 10, 20 và 70
giúp mình với mình cần gấp lắm rồi!^^
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\(a,ƯC\left(40,24\right)=Ư\left(8\right)=\left\{...\right\}\\ b,ƯC\left(12,52\right)=Ư\left(4\right)=\left\{...\right\}\\ c,ƯC\left(36,990\right)=Ư\left(18\right)=\left\{...\right\}\\ d,ƯC\left(54,36\right)=Ư\left(9\right)=\left\{...\right\}\\ e,ƯC\left(10,20,70\right)=Ư\left(10\right)=\left\{...\right\}\\ f,ƯC\left(25,55,75\right)=Ư\left(5\right)=\left\{...\right\}\\ g,ƯC\left(80,144\right)=Ư\left(16\right)=\left\{...\right\}\\ h,ƯC\left(63,2970\right)=Ư\left(9\right)=\left\{...\right\}\\ i,ƯC\left(65,125\right)=Ư\left(5\right)=\left\{...\right\}\\ j,ƯC\left(9,18,72\right)=Ư\left(9\right)=\left\{...\right\}\\ k,ƯC\left(24,36,60\right)=Ư\left(12\right)=\left\{...\right\}\\ l,ƯC\left(16,42,86\right)=Ư\left(2\right)=\left\{..\right\}\)
x + y = 36 (1)
2x - y = 12
Áp dụng phương pháp cộng đại số
<=> x + 2x = 36 + 12
<=> 3x = 48
<=> x = 16
Thế x = 16 vào pt (1) => y = 20
a) Gọi \(d\inƯC\left(n+1;2n+3\right)\)
\(\Leftrightarrow\left\{{}\begin{matrix}n+1⋮d\\2n+3⋮d\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}2n+2⋮d\\2n+3⋮d\end{matrix}\right.\)
\(\Leftrightarrow2n+2-2n-3⋮d\)
\(\Leftrightarrow-1⋮d\)
\(\Leftrightarrow d\inƯ\left(-1\right)\)
\(\Leftrightarrow d\in\left\{1;-1\right\}\)
\(\LeftrightarrowƯC\left(n+1;2n+3\right)=\left\{1;-1\right\}\)
\(\LeftrightarrowƯCLN\left(n+1;2n+3\right)=1\)
hay n+1 và 2n+3 là cặp số nguyên tố cùng nhau(đpcm)
\(a,\dfrac{52}{32}=\dfrac{13}{8}\\ \dfrac{55}{65}=\dfrac{11}{13}\\ MSC:104\\ =>\dfrac{13}{8}=\dfrac{13.13}{8.13}=\dfrac{169}{104}\\ \dfrac{11}{13}=\dfrac{11.8}{13.8}=\dfrac{88}{104}\)
\(b,\dfrac{72}{64}=\dfrac{9}{8}\\ \dfrac{54}{81}=\dfrac{2}{3}\\ MSC:24\\ \dfrac{9}{8}=\dfrac{9.3}{8.3}=\dfrac{27}{24}\\ \dfrac{2}{3}=\dfrac{2.8}{3.8}=\dfrac{16}{24}\\ c,\dfrac{24}{36}=\dfrac{2}{3}\\ \dfrac{12}{30}=\dfrac{2}{5}\\ MSC:15\\ \dfrac{2}{3}=\dfrac{2.5}{3.5}=\dfrac{10}{15}\\ \dfrac{2}{5}=\dfrac{2.3}{3.5}=\dfrac{6}{15}\)
\(d,\dfrac{80}{40}=2\\ \dfrac{45}{63}=\dfrac{5}{7}\\ MSC:7\\ 2=\dfrac{14}{7}\\ e,\dfrac{150}{50}=3\\ \dfrac{100}{200}=\dfrac{1}{2}\\ MSC:2\\ 3=\dfrac{6}{2}\\ f,\dfrac{54}{81}=\dfrac{2}{3}\\ \dfrac{69}{93}=\dfrac{23}{21}\\ MSC:21\\ \dfrac{2}{3}=\dfrac{2.7}{3.7}=\dfrac{14}{21}\)
\(a.\dfrac{52}{32}\text{=}\dfrac{13}{8};\dfrac{55}{65}\text{=}\dfrac{11}{13}\)
\(\dfrac{13.13}{13.8}\text{=}\dfrac{169}{104};\dfrac{11.8}{13.8}\text{=}\dfrac{88}{104}\)
\(c.\dfrac{24}{36}\text{=}\dfrac{2}{3};\dfrac{12}{30}\text{=}\dfrac{2}{5}\)
\(\dfrac{2.5}{3.5}\text{=}\dfrac{10}{15};\dfrac{2.3}{5.3}\text{=}\dfrac{6}{15}\)
\(b.\dfrac{72}{64}\text{=}\dfrac{9.3}{8.3}\text{=}\dfrac{27}{24};\dfrac{54}{81}\text{=}\dfrac{2.8}{3.8}\text{=}\dfrac{16}{24}\)
\(d.\dfrac{80}{40}\text{=}\dfrac{2.63}{63}\text{=}\dfrac{126}{63};\dfrac{45}{63}\)
\(e.\dfrac{150}{50}\text{=}\dfrac{3.2}{2}\text{=}\dfrac{6}{2};\dfrac{100}{200}\text{=}\dfrac{1}{2}\)
\(f.\dfrac{54}{81}\text{=}\dfrac{2.31}{3.31}\text{=}\dfrac{62}{93};\dfrac{69}{93}\)
`2/9 + 6/27 + 8/36 + 12/54 + 16/72 + 18/81`
`= 2/9 + 2/9 + 2/9 + 2/9 + 2/9 + 2/9`
`= 2/9 xx 6`
`= 12/9 = 4/3`
đề bài là j đây bạn
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