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1996*1995-1996*1994=1996
(1996*1995-996)-(1996*1994)=1996-996=1000
(1996*1995-996)-(1996*1994+1000)=1996-996-1000=0
=>(1996*1995-996)/(1996*1994+1000)=1( vì tử số bằng mẫu số)
\(\frac{1996.1995-996}{1996.1994+1000}=\frac{\left(1000+996\right).1995-996}{\left(1000+996\right).1994+1000}\)
\(=\frac{1000.1995+996.1995-996}{996.1994+1000.1994+1000}=\frac{1000.1995+996\left(1995-1\right)}{996.1994+1000\left(1994+1\right)}\)
\(=\frac{1000.1995+996.1994}{996.1994+1000.1995}\)=1
a)4,25+3,15+3,75+5,85=(4,25+3,75)+(3,15+5,85)=8+9=17.
b)(3/5+4/7)+2/5=(3/5+2/5)+4/7=1+4/7=11/7.
c)6,24+5,36+3,76=(6,24+3,76)+5,36=10+5,36=15,36.
d)(19/15+3/5)+11/15=(19/15+11/15)+3/5=2+3/5=13/5.
ủng hộ nha có j kb vs mk
Tính bằng cách thuận tiện nhất:
a ) 4,25 + 3,15 + 3,75 + 5,85
= ( 4,25 + 3,75 ) + ( 3,15 + 5, 85 )
= 8 + 9
= 17
tks giúp mk vs ạ!
a,Đặt \(A=\frac{1}{1\times4}+\frac{1}{4\times7}+...+\frac{1}{97\times100}\)
\(\Rightarrow3A=\frac{3}{1\times4}+\frac{3}{4\times7}+...+\frac{3}{97\times100}\)
\(\Rightarrow3A=\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+...+\frac{1}{97}-\frac{1}{100}\)
\(\Rightarrow3A=1-\frac{1}{100}=\frac{99}{100}\)
\(\Rightarrow A=\frac{99}{300}\)
b, \(\frac{1}{2}\times\frac{2}{3}\times...\times\frac{99}{100}=\frac{1\times2\times...\times99}{2\times3\times...\times1000}=\frac{1}{100}\)
c, \(\frac{3}{4}\times\frac{8}{9}\times...\times\frac{99}{100}=\frac{1.3}{2.2}\times\frac{2.4}{3.3}\times...\times\frac{9.11}{10.10}=\frac{1.2.....9}{2.3.....10}\times\frac{3.4.....11}{2.3.....10}=\frac{1}{10}\times\frac{11}{2}=\frac{11}{20}\) (dấu . là dấu nhân)
\(A=\left(1-\frac{1}{97}\right)x\left(1-\frac{1}{98}\right)x....x\left(1-\frac{1}{1000}\right)\)
\(A=\frac{96}{97}x\frac{97}{98}x..x\frac{999}{1000}\)
\(A=\frac{96x97x98x...x999}{97x98x99x...x1000}=\frac{96}{1000}=\frac{12}{125}\)
Nguyễn Hiền Anh!
\(\frac{11}{9}+\frac{35}{18}\)
\(=\frac{19}{6}\)
\(\frac{22}{21}:\frac{1}{2}+\frac{25}{12}:\frac{1}{2}\)
\(\frac{44}{21}+\frac{25}{6}\)
\(\frac{263}{42}\)
\(a,\frac{125\cdot81\cdot7}{49\cdot75\cdot27}=\frac{25\cdot5\cdot9\cdot9\cdot7}{7\cdot7\cdot15\cdot5\cdot3\cdot9}=\frac{25\cdot9}{7\cdot15\cdot3}=\frac{5\cdot5\cdot3\cdot3}{7\cdot3\cdot5\cdot3}=\frac{5}{7}\)
\(b,\frac{48\cdot25-48\cdot11-48}{16\cdot23-16\cdot10}=\frac{1200-528-48}{368-160}=\frac{624}{208}=3\)
\(c,\frac{15\cdot\left[4\cdot17+17\cdot5\right]}{18\cdot25\cdot34}=\frac{15\cdot\left[17\cdot\left(4+5\right)\right]}{15300}=\frac{15\cdot153}{15300}\)
\(=\frac{2295}{15300}=\frac{3}{20}\)
\(d,\frac{1996\cdot1995-996}{1000+1996\cdot1994}=\frac{3982020-996}{1000+3980024}=\frac{3981024}{3981024}=1\)