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17 . 85 + 17 . 15 + 300
= 17 . ( 85 + 15 ) + 300
= 17 . 100 + 300
= 1 700 + 300
= 1 400
72 . 121 + 27 . 121 + 121
= 121 . ( 72 + 27 + 1 )
= 121 . 100
= 12 100
32 . 39 + 52 . 21 - 12 . 39 + 21 . 48
= 39 . ( 32 - 12 ) + 21 . ( 52 + 48 )
= 39 . 20 + 21 . 100
= 780 + 2 100
= 9 900
a.=17*(85+15)+300
=17*100+300
=1700+300=2000
b.=121*(72+27+1)
=121*100=12100
c.chịu
![](https://rs.olm.vn/images/avt/0.png?1311)
\(S=3^1+3^2+3^3+.....+3^{100}\) \(=\left(3^1+3^2+3^3+3^4\right)+\left(3^5+3^6+3^7+3^8\right)+...+\left(3^{97}+3^{98}+3^{99}+3^{100}\right)\)
\(=120+3^5.\left(3^1+3^2+3^3+3^4\right)+....+3^{97}.\left(3^1+3^2+3^3+3^4\right)\)
\(=1.120+3^5.120+...+3^{97}.120\)
\(=\left(1+3^5+...+3^{97}\right).120\)
\(\Rightarrow S⋮120\)
Vậy ........
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a, 134.53 +52.66+200.48
=134.(48+5)+(48+4).66+200.48
=134.48+134.5+48.66+4.66+200.48
=48.(134+66+200)+134.5+4.66
=48.400+670+246
=19200+916
=20116
còn lại cũng tương tự
134.53 + 52.66 + 200.48 = ( 52 + 48 ) . ( 134 + 66 ) . 53
= 100 . 200 + 50
= 20.000 + 200 + 50
=20.250
P/s: Tất cả cx tương tự như phép tính trên
![](https://rs.olm.vn/images/avt/0.png?1311)
17.70+17.45-17.15
=17.(70+45-15)
=17.100
=1700
6.3^3-162:3^2+2016^0
=6.27-162:9+1
=162-18+1
=45
17 . 70 + 17 . 45 - 17 . 15
= 17 . (70 + 45 - 15)
= 17 . 100
= 1700
\(6 . 3^3 - 162 : 3^2 + 2016^0\)
= 6 . 27 - 162 : 9 + 1
= 162 - 18 + 1
= 144 + 1
= 145
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(17\cdot85+15\cdot17-120\)
\(=17\cdot\left(85+15\right)-120\)
\(=17\cdot100-120\)
\(=1700-120\)
\(=1580\)
b) \(27\cdot77+24\cdot27-27\)
\(=27\cdot\left(77+24-1\right)\)
\(=27\cdot100\)
\(=2700\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(17\cdot85+15\cdot17+2^3\cdot3\cdot5\)
\(=17\cdot100+40\cdot3\)
\(=1700+120=1820\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(17.85+15.17-120\)
\(=17.\left(15+85\right)\)\(-120\)
\(=17.100-120\)
\(=1700-120\)
\(=1580\)
17.85+15.17-120
=17.(15+85)-120
=17.100-120
=1700-120
=1580
K cho mk nha
![](https://rs.olm.vn/images/avt/0.png?1311)
17.85+17.15-120
= 17 . ( 85 + 15 ) - 120
= 17 . 100 = 120
= 1700 - 120
= 1580
= 1580