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a) 4567 + (1234 – 4567) -4
= 4567 + 1234 - 4567 -4
= ( 4567-4567) + ( 1234 -4)
= 0+1230
=1230
(-29).(85-47)-85.(47-29)
=(-29).85+29.47-85.47+85.29
=85.[(-29)+29]+47.(29-85)
=85.0+47.(-56)
=0+(-2632)
(-167) . (67-34) - 67 . ( 34- 167)
=-167.67+167.34 - 67.34+67.167
=167.34-67.34
=34.(167-67)
=34.100=3400
c; 37.(24 - 77) - 24.(37 - 77)
= 37.24 - 37.77 - 24.37 + 24.77
= (37.24 - 24.37) - (37.77 - 24.77)
= 0 - 77.(37 - 24)
= - 77 . 13
= - 1001
A,153.177-153.77+100.(-77)
=153.(177-77)+100.(-77)
=153.100+100.(-77)
=100.(153+(-77))
=100.76
=7600
a)153.177-153.77+100+100.(-77)
=153.(177-77)+100.[1+(-77)]
=153.100+100.(-76)
=100.[153+(-76)]
=100.77=7700
b)(-29).(85-47)-85.(47-29)
=(-29).85+29.47-85.47+85.29
=85.[(-29)+29]+47.(29-85)
=85.0+47.(-56)
=0+(-2632)
c)(-167) . (67-34) - 67 . ( 34- 167)
=-167.67+167.34 - 67.34+67.167
=167.34-67.34
=34.(167-67)
=34.100=3400
\(A=\frac{1}{25.27}+\frac{1}{27.29}+\frac{1}{29.31}+...+\frac{1}{83.85}\)
\(\Rightarrow2A=\frac{2}{25.27}+\frac{2}{27.29}+\frac{2}{29.31}+...+\frac{2}{83.85}\)
\(2A=\frac{1}{25}-\frac{1}{27}+\frac{1}{27}-\frac{1}{29}+\frac{1}{29}-\frac{1}{31}+...+\frac{1}{83}-\frac{1}{85}\)
\(2A=\frac{1}{25}-\frac{1}{85}\)
\(2A=\frac{12}{425}\)
\(A=\frac{12}{425}:2\)
\(A=\frac{6}{425}\)
\(C=\frac{2}{15}+\frac{2}{35}+\frac{2}{63}+...+\frac{2}{399}\)
\(C=\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+...+\frac{2}{19.21}\)
\(C=\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+...+\frac{1}{19}-\frac{1}{21}\)
\(C=\frac{1}{3}-\frac{1}{21}\)
\(C=\frac{2}{7}\)
CÂU B LÀM TƯƠNG TỰ NHA
HOK TOT
(85+106+17)-(85+19)
=97
b 3x+27=45
3x=45-27
3x=18
x=18:3
x=6
vậy......
c ) 29.(15-34) -15 .(29-34)
=29.15-29.34-15.29+15.34
=-476