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( 3 19 . 4 + 5 . 3 19 ) : 3 21
= [ 3 19 . ( 4 + 5 ) ] : 3 21
= ( 3 19 . 9 ) : 3 21
= ( 3 19 . 32 ) : 3 21
= 3 21 : 321
= 1
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![](https://rs.olm.vn/images/avt/0.png?1311)
\(19\cdot\left(-8\right)+19\cdot\left(-2\right)=19\cdot\left(-8+-2\right)=19\cdot-10=-190\)
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1: \(\dfrac{-7}{4}\cdot\dfrac{2}{9}=\dfrac{-14}{36}=\dfrac{-7}{18}\)
2: \(=\dfrac{12}{13}\cdot\dfrac{26}{5}=\dfrac{24}{5}\)
3: \(=\dfrac{20}{11}\cdot\dfrac{55}{21}=\dfrac{100}{21}\)
4: \(=\dfrac{-40}{240}=\dfrac{-1}{6}\)
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1/ 1 + (-2) + 3 + (-4) + . . . + 19 + (-20)
=1-2+3-4+...+19-20
=(1-2)+(3-4)+...+(19-20)
=(-1)+(-1)+...+(-1)
=(-1).10
=-10
2/ 1 – 2 + 3 – 4 + . . . + 99 – 100
=(1-2)+(3-4)+...+(99-100)
=(-1)+(-1)+...+(-1)
=(-1).50
=-50
3/ 2 – 4 + 6 – 8 + . . . + 48 – 50
=(2-4)+(6-8)+...+(48-50)
=(-2)+(-2)+...+(-2)
=(-2).13
=-26
4/ – 1 + 3 – 5 + 7 - . . . . + 97 – 99
=(-1)+(3-5)+(7-9)+...+(97-99)
=(-1)+(-2)+(-2)+...+(-2)
=(-1)+(-2).45
=(-1)+(-90)
=(-91)
5/ 1 + 2 – 3 – 4 + . . . . + 97 + 98 – 99 - 100
=(1+2-3-4)+...+(97 + 98 – 99 - 100)
=(-4)+...+(-4)
=(-4).25
=-100
\(HT\)
1/ \(1+(-2)+3+(-4)+...+19+(-20)\)
\(=(-1+3+5+...+19)-(2+4+6+...+20)\)
\(=(19-1):2+1=10\)
\(=(1+19).10:2-(20+2).10:2\)
\(=100-110\)
\(=-10\)
2/ \(1 – 2 + 3 – 4 + . . . + 99 – 100\)
\(= ( 1 - 2 ) + ( 3 - 4) + .... + ( 99 - 100 )\)
\(= -1 + ( -1) + ....+ ( -1)\)
\(=(-1).50\)
\(=-50\)
3/ \( 2 – 4 + 6 – 8 + . . . + 48 – 50\)
\(= 2 +( – 4 + 6)+( – 8+10) + . . . +( -44+46)+ ( 48 – 50)\)
\(= 2+2+2+...+2+( -2) \)
\(= 2.12 +( -2 ) \)
\(=22\)
4/ \(-1+3-5+7-...+97-99\)
\(= ( -1 + 3 ) + ( -5 + 7 )+....+( -93 +95 ) + ( 97 - 99 )\)
\(= -2+( -2)+...+( -2)+2\)
\(= -2.24+2\)
\(=-46\)
5/ \( 1+2-3-4+...+97+98-99-100\)
\(= ( 1+2-3-4)+...+( 97+98-99-100)\)
\(= -4+...+( -4)\)
\(=(-4).25\)
\(=-100\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(2013.2014+2014.2015+2015.2016\right).\left(1+\frac{1}{3}-1-\frac{1}{3}\right)\)
\(=\left(2013.2014+2014.2015+2015.2016\right).0\)
= 0
![](https://rs.olm.vn/images/avt/0.png?1311)
A=4+22 +23+24+....220
A=22+22 +23 +24 +....220
2A=2(4+22 +23 +24 +....220)
2A=23+23 +24 +25 +....221
2A-A=(23+23 +24 +25 +....221)-(22+22 +23 +24 +....220)
A=23+221-(22+22)
A=8+221 - 8
A=221
Vậy A= 221
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Trả lời:
\(369-4\times\)\(\left[\left(-5\right)+4\times\left(-8\right)\right]\)
\(=369-4\times\left[\left(-5\right)+\left(-32\right)\right]\)
\(=369-4\times\left(-37\right)\)
\(=369-\left(-148\right)\)
\(=517\)
Hok tốt!
Vuong Dong Yet
369 - 4 . [(-5) + 4 .(-8) ]
= 369 - 4 . [ -5 + (-32) ]
= 369 - 4 . (-37)
= 369 - (-148)
= 369 + 148
= 517
= [ 1 + ( -2 ) ] + [ 3 + ( -4 ) ] + .... + [ 19 + ( -20 ) ] ( 10 cặp )
= ( -1 ) + ( -1 ) + ... + ( -1 )
= ( -1 ) x 10
= -10
=[1+(-2)] +[3+(-4)]+....+[19+(-20)]
=-1+(-1)+...+(-1)[10 số hạng (-1)]
=-1.10=-10