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![](https://rs.olm.vn/images/avt/0.png?1311)
a) (-124) + 24 = -100
b) 37. 78 + 37. 22
= 37 . ( 78 + 22 )
= 37 . 100
= 3700
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{\dfrac{5}{3}-\dfrac{5}{7}+\dfrac{5}{9}}{\dfrac{10}{3}-\dfrac{10}{7}+\dfrac{10}{9}}=\dfrac{5\left(\dfrac{1}{3}-\dfrac{1}{7}+\dfrac{1}{9}\right)}{10\left(\dfrac{1}{3}-\dfrac{1}{7}+\dfrac{1}{9}\right)}=\dfrac{1}{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
e: =5/7(5/11+2/11-14/11)
=5/7(-7/11)=-5/11
f: =-5/4(2/11+9/11)+1+3/4
=-5/4+7/4
=2/4=1/2
g: =-5/7(3/13+10/13)+1+5/7
=-5/7+1+5/7
=1
h: =7/4(29/5-9/5)+41/13
=-7+41/13=-50/13
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=2019^2-\left(2019-3\right)\left(2019+3\right)\\ A=2019-2019^2-2019\cdot3+2019\cdot3+3^2\\ A=9\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 35.34 + 35.86 + 65.75 + 65.45 =
( 35 + 65 ) x ( 34 + 86 ) + ( 75 + 45 )
100 x 120 x 120
100 x 14400
1440000
\(35\cdot34+35\cdot86+65\cdot75+65\cdot45\\ =35\cdot\left(34+86\right)+65\cdot\left(75+45\right)\\ =35\cdot120+65\cdot120\\ =120\cdot\left(35+65\right)\\ =120\cdot100\\ =12000\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Số số hạng của dãy là : (397−1):4+1=100(397-1):4+1=100 ( số )
⇒⇒ Có 100:2=50100:2=50 ( cặp )
1−5+9−13+....+393−3971-5+9-13+....+393-397
=(1−5)+(9−13)+....+(393−397)=(1-5)+(9-13)+....+(393-397)
=(−4)+(−4)+....+(−4)=(-4)+(-4)+....+(-4)
=(−4).50=−200=(-4).50=-200
TK`1-5+9-13+...+393-397`
`=(1-5)+(9-13)+...+(393-397)` (197 cặp)
`=(-4)+(-4)+...+(-4)`
`=(-4) xx 197`
`=-788`
![](https://rs.olm.vn/images/avt/0.png?1311)
11 + (- 7) . 12 + (- 48) : (- 4) + 52
= 11 + (- 84) + 12 + 25
= - 73 + 37
= - 36
2.17.12+2.6.21+8.3.62
= ( 2.12 ). 17+ ( 4.6).21+ (8.3).62
= 24.17+ 24.21+ 24.62
= 24. ( 17+ 21+62 )
= 24. 100
= 2400
= ( 2.12 ). 17+ ( 4.6).21+ (8.3).62
= 24.17+ 24.21+ 24.62
= 24. ( 17+ 21+62 )
= 24. 100
= 2400