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`a: =(7/3-4/3)+11/5=16/5`
`b: =(18/13-5/13)+55/46=1+55/46=101/46`
`c: =27/25-4/9-2/25+5/9=(27/25-2/25)+(5/9-4/9)=1+1/9=10/9`
A = \(\dfrac{1\times2\times3\times4\times5\times6\times....\times100\times101}{3\times4\times5\times6\times.......\times100}\)
A = 1 x 2 x 101 x \(\dfrac{3\times4\times5\times6\times........\times100}{3\times4\times5\times6.............\times100}\)
A = 1 x 2 x 101 x 1
A = 202
\(\dfrac{1.2.3.4.5....101}{3.4.5.6.100}\)
Ta thấy phần tử sẽ triệt tiêu hết cho mẫu nên mẫu sẽ bằng 1
=> \(\dfrac{2.101}{2}=202\)
`a, 4/9 + 2/5 + 5/9= (4/9 +5/9) + 2/5= 1 + 2/5= 5/5 + 2/5= 7/5`
`b, 6/13 + 5/8 + 7/13=(6/13 + 7/13) + 5/8=1+5/8= 8/8 + 5/8= 13/8`
`c, 5/11 + 6/25 + 66/121 = ( 5/11 + 66/121 ) + 6/25=1 + 6/25 = 25/25 + 6/25 = 31/25`
`d, 1/2 + 1/3 + 1/4 + 1/6 + 1/12 + 1/24= (1/2 + 1/4) +(1/3 + 1/6) + (1/12 + 1/24)= 3/4 + 1/2 + 1/8= 6/8 + 4/8 + 1/8= 11/8`
`@ yl`
Bạn tự làm bài nếu bạn không tính được thì bạn hỏi cô hay thầy đấy nha bạn,chúc bạn học giỏi nha:
a, \(\frac{39}{19}\)
b, \(8.5\)hay \(\frac{17}{2}\)
c, \(\frac{1277}{4186}\)
Bấm máy tính là được ^_^
\(.\)
A) 3\7 + 5\9 +4\7+ 4\9=(3\7+4\7) + ( 5\9 +4\9) = 7\7+9\9=63\63+63\63=126\63=42\21
b) 1\5+4\11+4\5+ 7\11=(1\5+4\5)+ (4\11+7\11)=5\5+11\11=55\55+55\55=110\55=22\11
Bài 1:
a) 19/27+9/7+6/27+5/7+2/7
= (19/27+6/27) + (9/7+5/7+2/7)
=1 + 16/7
=23/7
b) 2/7 + 27/48 + 7/16 +45/63
= (2/7 + 45/63) + (27/48 +7/16)
= (2/7 + 5/7) + ( 9/16 + 7/16)
= 1 + 1
=2
c) Tính bằng cách bình thường
Bài 2:
6/11 + x = 1
x = 1-6/11
x = 5/11
Bài làm
a) \(\frac{19}{27}+\frac{9}{7}+\frac{6}{27}+\frac{5}{7}+\frac{2}{7}\)
\(=\frac{27}{27}+\frac{16}{7}\)
\(=1+\frac{16}{7}\)
\(=\frac{7}{7}+\frac{16}{7}\)
\(=\frac{23}{7}\)
b) \(\frac{2}{7}+\frac{27}{48}+\frac{7}{16}+\frac{45}{63}\)
\(=\left(\frac{18}{63}+\frac{45}{63}\right)+\left(\frac{27}{48}+\frac{21}{48}\right)\)
\(=\frac{63}{63}+\frac{48}{48}\)
\(=1+1\)
\(=2\)
c) \(\frac{17}{23}+\left(\frac{4}{7}-\frac{6}{13}\right)\)
\(=\frac{17}{23}+\left(\frac{52}{91}-\frac{42}{91}\right)\)
\(=\frac{17}{23}+\frac{10}{91}\)
\(=\frac{1547}{2093}+\frac{230}{2093}\)
\(=\frac{1770}{2093}\)
Bài 2
\(\frac{6}{11}+x=1\)
\(x=1-\frac{6}{11}\)
\(x=\frac{11}{11}-\frac{6}{11}=\frac{5}{11}\)
Vậy \(x=\frac{5}{11}\)
7/21 + 125/75 + 14/21 + 25/175
= 1/3 + 5/3 + 2/3 + 1/7
= 8/3 + 1/7
= 59/21
\(A=\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\)
\(=\frac{1}{2}-\frac{1}{8}=\frac{3}{8}\)
\(\dfrac{19}{4}+\dfrac{25}{3}-\dfrac{11}{4}+\dfrac{2}{3}\)
\(=\left(\dfrac{19}{4}-\dfrac{11}{4}\right)+\left(\dfrac{25}{3}+\dfrac{2}{3}\right)\)
\(=\dfrac{8}{4}+\dfrac{27}{3}\)
\(=2+9\)
\(=11\)
\(\dfrac{19}{4}+\dfrac{25}{3}-\dfrac{11}{4}+\dfrac{2}{3}\)
\(=\left(\dfrac{19}{4}-\dfrac{11}{4}\right)+\left(\dfrac{25}{3}+\dfrac{2}{3}\right)\)
\(=\dfrac{8}{4}+\dfrac{27}{3}\)
\(=2+9=11\)