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\(-1999.19981998+19991999.1998\)
\(=-1999.\left(19980000+1998\right)+1998.\left(19990000+1999\right)\)
\(=-1999.19980000-1999.1998+1998.19990000+1998.1999\)
\(=\left(1998.1999-1999.1998\right)+\left(1998.19990000-1999.19980000\right)\)
\(=\left(1998.1999-1999.1998\right)+10000\left(1998.1999-1999.1998\right)=0\)
=-1999.1998.10 001+1999.10 001.1998
=(-1999+1999).1998.10 001
=0.1998.10 001=0
-1999.19981998+19991999.1998
=-1999.1998.10001+1999.10001.1998
=1998.10001(-1999+1999)
=1998.10001.0
=0
\(C=\frac{5}{1.3}+\frac{5}{3.5}+\frac{5}{5.7}+...+\frac{5}{997.999}\)
\(\Leftrightarrow C=\frac{5}{2}\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+...+\frac{2}{997.999}\right)\)
\(\Leftrightarrow C=\frac{5}{2}\left(\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{997}-\frac{1}{999}\right)\)
\(\Leftrightarrow C=\frac{5}{2}\left(1-\frac{1}{999}\right)=\frac{5}{2}.\frac{998}{999}=\frac{2495}{999}=2\frac{497}{999}\)
\(A=\frac{2}{4}+\frac{2}{28}+\frac{2}{70}+\frac{2}{130}+\frac{2}{208}\)
\(\Leftrightarrow A=\frac{2}{1.4}+\frac{2}{4.7}+\frac{2}{7.10}+\frac{2}{10.13}+\frac{2}{13.16}\)
\(\Leftrightarrow A=\frac{2}{3}\left(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+\frac{3}{10.13}+\frac{3}{13.16}\right)\)
\(\Leftrightarrow A=\frac{2}{3}\left(\frac{1}{1}-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-\frac{1}{13}+\frac{1}{13}-\frac{1}{16}\right)\)
\(\Leftrightarrow A=\frac{2}{3}\left(1-\frac{1}{16}\right)=\frac{2}{3}.\frac{15}{16}=\frac{5}{8}\)
C = 5/1x3 + 5/3x5 + 5/5x7 + ... + 5/997x999
C = 5 - 5/3 + 5/3 - 5/5 + 5/5 - 5/7 + ... + 5/997 - 5/999
C = 5 - 5/999
C = bạn tự tính nhé !
A = 2/4 + 2/28 + 2/70 + 2/130 + 2/208
A = 2/1x4 + 2/4x7 + 2/7x10 + 2/10x13 + 2/13x16
A = 2 - 2/4 + 2/4 - 2/7 + 2/7 - 2/10 + 2/10 - 2/13 + 2/13 - 2/16
A = 2 - 2/16
A = bạn tự tính nhé !
12000 - ( 1500 . 2 + 1800 . 3 + 1800 . 2 : 3 )
= 12000 - ( 3000 + 5400 + 3600 : 3 )
= 12000 - ( 3000 + 5400 + 1200 )
= 12000 - 9600
= 2400
12 000 - (1500 . 2 + 1800 . 3 + 1800 . 2 : 3)
=12 000 - (3000 + 5400 + 3600 : 3)
= 12 000 - (3000 + 5400 + 1200)
= 12 000 - 9600 = 2400
Bài làm
A = [(-88) - 48 + 82 ] - [ -48 + 82 + 58 ]
A = (-88) - 48 + 82 - 48 - 82 - 58
A = [ ( -88 ) + 58 ] - ( 48 - 48 ) - ( 82 - 82 )
A = -30 - 0 - 0
A = -30
# Chúc bạn học tốt #
A = [(-88) - 48 + 82] - [-48 + 82 + 58]
= -88 - 48 + 82 + 48 - 82 - 58
= (-48 + 48) + (82 - 82) + (-88 - 58)
= 0 + 0 - 146
= -146
19.64+76.34 35.12+65.13
=19.64+19.4.34 =35.12+65.(12+1)
=19.64+19.136 =35.12+65.12+65.1
=19.(64+136) =35.12+65.12+65
=19.200 =12.(35+65)+65
=3800 =12.100+65
=1200+65
=1265
1.(-1999).19981998+19991999.1998
=(-1998-1).19981998+19991999.1998
=(-1998).19981998-19981998+19991999.1998
=(-19981998+19991999).1998-19981998
=10001.1998-19981998
=0