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B= 1.99+2.98+2.97+...98.2+99.1
=1.99+2.(99-1)+3.(99-2)+...+98.(99-97)+99.(99-98)
=1.99+2.99-1.2+3.99-2.3+...+98.99-97.98+99.99-98.99
=(1.99+2.99+3.99+...+98.99+99.99)-(1.2+2.3+3.4+...+97.98+98.99)
=99.(1+2+3+...+98+99)-(1.2+2.3+3.4+...+97.98+98.99)
=99.4950-(1.2+2.3+3.4+...+97.98+98.99)
=490050-(1.2+2.3+3.4+...+97.98+98.99)
Đặt C=1.2+2.3+3.4+...+97.98+98.99
=> 3C=1.2.3+2.3.3+3.4.3+...+97.98.3+98.99.3
=1.2.3+2.3.(4-1)+...+98.99.(100-97)
=1.2.3+2.3.4-1.2.3+...+98.99.100-97.98.99
=98.99.100
=> A=(98.99.100):3=323400
Vậy B=490050-323400=166650
=1.99+2.(99-1)+3.(99-2)+4.(99-3)+......+99.(99-98)
=99.(1+2+3+.......+99)-(2+2.3+3.4+........+98.99)
=99.(1+99).99:2-98.99.100:3
=99.50.99-98.33.100
=490050-323400=166650
-48+48.(-78)+48.(-21)
= 48.[ (-1) +(-78) + (-21)]
= 48.(-100)
= -4800
=100x(99-98)
=100x1=100
kết bạn với mình nha!
\(-48+48\times\left(-78\right)+48\times\left(-21\right)\)
\(=48\times\left(-1\right)+48\times\left(-78\right)+48\times\left(-21\right)\)
\(=48\left[\left(-1\right)+\left(-78\right)+\left(-21\right)\right]\)
\(=48\times\left(-100\right)=-4800\)
A)2.125.2002.8.5=(125.8).(2.5).2002. C)28.47+28.43+72.29+72.61 D)26.54+52.73
=1000.10.2002=10000.2002=20020000 =28.(47+43)+72.(29+61) =26.27.2+52.73
B)36.42+2.17.18+9.41.6=36.42+(2.18).17+9.41.6 =28.90+72.90 =(26.2).27+52.73
= 36.42 +2.17.18+41 .54 =90.(28+72) =52.27+52.73
=(36+54).(42+18).(41+2+17)=90.60.60=324000 =90.100=9000 =52.(27+73)=52.100=5200
đơn giản!!!
a) 18, 42
18 = 2 . 3\(^2\)
42 = 2 . 3 . 7
ƯCLN(18, 42) = 2 . 3\(^2\)= 18
b) 28, 48
28 = 2\(^2\). 7
48 = 2\(^4\). 3
ƯCLN(28, 48) = 2\(^4\)= 16
chúc may mắn!
-48+48x(-78)+48x(-21)
=48x(-1-78-21)
=48x(-100)
=-4800
\(=-48+48\times\left(-78\right)+48\times\left(-21\right)\)
\(=48\times\left(-1-78-21\right)\)
\(=48\times\left(-100\right)\)
\(=-4800\)