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\(A=\dfrac{1997\times1996-1}{1995\times1997+1996}=\dfrac{1997\times\left(1995+1\right)-1}{1995\times1997+1996}=\dfrac{1995\times1997+1997-1}{1995\times1997+1996}=\dfrac{1995\times1997+1996}{1995\times1997+1996}=1\)
\(\frac{1997.1996-97}{1995.1997-1000}=\frac{1997.1995+1997-97}{1997.1995-1000}=\frac{1997.1995-1000}{1997.1995-1000}=1\)
\(\frac{1997\times1996-97}{1995\times1997-1000}=\frac{1997\times1995+1997-97}{1997\times2995+1000}=\frac{1997\times1995+1000}{1997\times1995+1000}=1\)
a) \(\dfrac{1997x1996-1}{1995x1997+1996}=\dfrac{1997x\left(1995+1\right)-1}{1995x1997+1996}\)
\(=\dfrac{1997x1995+1997-1}{1995x1997+1996}=\dfrac{1997x1995+1996}{1995x1997+1996}=1\)
b) \(\dfrac{1997x1996-995}{1995x1997+1002}=\dfrac{1997x\left(1995+1\right)-995}{1995x1997+1002}\)
\(=\dfrac{1997x1995+1997-995}{1995x1997+1002}=\dfrac{1997x1995+1002}{1995x1997+1002}=1\)
1995x(1996+1)-998
997+1995x1996
=>
1995x(1996+1)-998
997+1995x1996
=>
1995x1996+1995-998
997+1995x1996
=>1995x1996+997
997+1995x1996
=1
Ta có :
\(\frac{1995.1997-1}{1996.1995+1994}\)
\(=\frac{1995.\left(1996+1\right)-1}{1995.1996+1994}\)
\(=\frac{1995.1996+1995-1}{1995.1996+1994}\)
\(=\frac{1995.1996+1994}{1995.1996+1994}=1\)
Ủng hộ mk nha !!! ^_^
\(\frac{1995x1997-1}{1996x1995+1994}\)
\(=\frac{1995x1996+1995-1}{1996x1995+1994}\)
\(=\frac{1995x1996+1994}{1996x1995+1994}=1\)
a.=7-(1/1x2 + 1/2x3 + 1/3x4 + 1/4x5 + 1/5x6 + 1/6x7 + 1/7x8 )
= 7- [ 1 - 1/8 ]
= 7 - 7/8
= 49/8
b.=1997x 1995 + 1997 - 995 / 1997 x 1995 + 1002
=1997-995/1002
=1
còn câu cuối để mình nghĩ
\(E=\frac{1}{2}+\frac{5}{6}+\frac{11}{12}+\frac{19}{20}+\frac{29}{30}+\frac{41}{42}+\frac{55}{56}\)
\(E=\frac{1}{2}+\frac{6-1}{6}+\frac{12-1}{12}+\frac{20-1}{20}+\frac{30-1}{30}+\frac{42-1}{42}+\frac{56-1}{56}\)
\(E=\frac{1}{2}+\frac{6}{6}-\frac{1}{6}+\frac{12}{12}-\frac{1}{12}+\frac{20}{20}-\frac{1}{20}+\frac{30}{30}-\frac{1}{30}+\frac{42}{42}-\frac{1}{42}+\frac{56}{56}-\frac{1}{56}\)
\(E=\frac{1}{1x2}+1+1+1+1+1+1-\left(\frac{1}{2x3}+\frac{1}{3x4}+\frac{1}{4x5}+\frac{1}{5x6}+\frac{1}{6x7}+\frac{1}{7x8}\right)\)
\(E=1-\frac{1}{2}+6-\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\right)\)
\(E=1-\frac{1}{2}+6-\left(\frac{1}{2}-\frac{1}{8}\right)\)
\(E=1-\frac{1}{2}+6-\frac{1}{2}+\frac{1}{8}\)
\(E=6+\frac{1}{8}=\frac{49}{8}\)
\(\frac{1997x1996-995}{1995x1997+1002}=\frac{1997x\left(1995+1\right)-995}{1995x1997+1002}\)
\(=\frac{1997x1995+1997x1-995}{1995x1997+1002}\)
\(=\frac{1997x1995+1997-995}{1995x1997+1002}\)
\(=\frac{1997x1995+1002}{1995x1997+1002}=1\)