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a) 1313/2121 . 165165/143143 . 424242/151515
= 13/21 . 15/13 . 14/5
= 2
Ps: Rút gọn tới tối giản r tính dễ hơn ế. ;)
\(\frac{1997\times1996-1}{1995\times1997+1996}\)
\(=\frac{1997\times\left(1995+1\right)-1}{1995\times1997+1996}\)
\(=\frac{1997\times1995+1997-1}{1995\times1997+1996}\)
\(=\frac{1997\times1995+1996}{1995\times1997+1996}=1\)
\(\frac{-1997.1996+1}{\left(-1995\right).\left(-1997\right)+1996}=\frac{-1997\left(1995+1\right)+1}{1995.1997+1996}\)
\(=\frac{-1997.1995+\left(-1997\right)+1}{1995.1997+1996}=\frac{-1997.1995+\left(-1996\right)}{1995.1997+1996}=-1\)
rut gon con 1/-1995 vi rut gon 1996 ca tu va mau
rut gon -1997 ca tu va mau cung deu co vi vay sau khi rut gon cac so giong nh au thi phan so tren con 1/-1995
\(\frac{-1997\cdot1996+1}{-1995\cdot\left(-1997\right)+1996}\)
\(=\frac{-1997\cdot\left(1995+1\right)+1}{1995\cdot1997+1996}\)
\(=\frac{-1997\cdot1995+\left(-1997\right)+1}{1995\cdot1997+1996}\)
\(=\frac{-1997\cdot1995+\left(-1996\right)}{1995\cdot1997+1996}\)
\(=-1\)
\(\frac{-1997.1996+1}{-1995.\left(-1997\right)+1996}\)
\(=\frac{-1997.1996+1}{1995.1997+1996}\)
\(=\frac{-1997.\left(1995+1\right)+1}{1995.1997+1996}\)
\(=\frac{-1997.1995+-1997+1}{1995.1997+1996}\)
\(=\frac{1995.-1997+-1996}{1995.1997+1996}\)
\(=\frac{-\left(1995.1997+1996\right)}{1995.1997+1996}\)
\(=-1\)
a: \(\dfrac{-315}{540}=\dfrac{-315:45}{540:45}=\dfrac{-7}{12}\)
b: \(\dfrac{25\cdot13}{26\cdot35}=\dfrac{25}{35}\cdot\dfrac{1}{2}=\dfrac{5}{7}\cdot\dfrac{1}{2}=\dfrac{5}{14}\)
\(a,\frac{1995}{1996}.\frac{19961996}{19311931}.\frac{193119311931}{199519951995}\) \(c,\frac{1997.1996-1}{1995.1997+1996}\)
\(=\frac{1995}{1996}.\frac{1996}{1931}.\frac{1931}{1995}\) \(=\frac{1997.\left(1995+1\right)-1}{1995.1997+1996}\)
\(=\frac{1995.1996.1931}{1996.1931.1995}\) \(=\frac{1997.1995+1997-1}{1997.1995+1996}\)
\(=1\) \(=\frac{1997.1995+1996}{1995.1997+1996}\)
\(=1\)
Ý (a) giống ý (b)
Ý (c) giống ý (d)