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\(65.59+65.42-13.5\)
\(\Rightarrow65.59+65.42-65\)
\(\Rightarrow65\left(59+42-1\right)=65.100=6500\)
65 . 59 + 65 . 42 - 13 . 5
= 65 . 59 + 65 . 42 - 65
= 65 . 59 + 65 . 42 - 65 . 1
= 65 . (59 + 42 - 1)
= 65 . 100
= 6500
#Học tốt!!!
~NTTH~
65 . 59 + 65 . 42 - 13 . 5
= 65 . 59 + 56 . 42 - 65
= 65 . ( 59 + 42 - 1 )
= 65 . 100
= 6500
65 . 59 + 65 . 42 - 13 . 5
= 65 . 59 + 56 . 42 - 65
= 65 . ( 59 + 42 - 1 )
= 65 . 100
= 6500
a) 2x : 22 = 3.23 + 23
2x-2 = 23.(3+1) = 23.4=23.22 = 25
=> x -2 = 5
x = 7
b) 65.59+65.42 - 13.5
= 65.(59+42) - 13.5
= 65.101 - 13.5
= 65.101- 65
= 65.(101-1) = 65.100 = 6500
45-[(18-15)2 + 24 ]
= 45 - (32 + 24) = 45 - 25 = 20
\(=45-\left(3^2+2^4\right)=45-\left(9+16\right)=45-25=20\)
b)\(=50+\left(30-2\left(14-3\right)\right)=50+\left(30-22\right)=50+8=58\)
I, 65.5+65.42-65=6500
II,
1,420-6x=330
<=>-6x=-90
<=>x=15
2, 10+2x=65536
<=>2x=65526
<=>x=32763
3, 37-2x-10=9
<=>-2x=-18
x=9
III, 2333<3222
Bài 1 .
65 . 59 - 65 . 42 - 65
= 65 . ( 59 - 42 ) - 65
= 65 . 17 - 65
= 1105 - 65
= 1040
Bài 2 .
a) 6 . ( 70 - x ) = 330
<=> 70 - x = 330 : 6
<=> 70 - x = 55
<=> x = 70 - 55
<=> x = 15
Vậy x = 15
b) 10 + 2x = 45 : 43
<=> 10 + 2x = 42
<=> 10 + 2x = 16
<=> 2x = 16 - 10
<=> 2x = 6
<=> x = 6 : 2
<=> x = 3
Vậy x = 3.
c) 37 - 2( x + 5 ) = 9
<=> 2( x + 5 ) = 37 - 9
<=> 2( x + 5 ) = 28
<=> x + 5 = 28 : 2
<=> x + 5 = 14
<=> x = 14 - 5
<=> x = 9
Vậy x = 9.
\(65.59+65.41-32.4\)
\(=65.\left(59+41\right)-32.4\)
\(=65.100-128\)
\(=6500-128\)
\(=6372\)
65.59+65.41-32.4
=65.(59+41).32-4
=65.100.28
=6500.28
=176000
\(\left(1+\dfrac{1}{1\cdot3}\right)\left(1+\dfrac{1}{2\cdot4}\right)\left(1+\dfrac{1}{3\cdot5}\right)\cdot...\cdot\left(1+\dfrac{1}{2019\cdot2021}\right)\)
\(=\left(1+\dfrac{1}{2^2-1}\right)\left(1+\dfrac{1}{3^2-1}\right)\cdot...\cdot\left(1+\dfrac{1}{2020^2-1}\right)\)
\(=\dfrac{2^2}{\left(2-1\right)\left(2+1\right)}\cdot\dfrac{3^2}{\left(3-1\right)\left(3+1\right)}\cdot...\cdot\dfrac{2020^2}{\left(2020-1\right)\left(2020+1\right)}\)
\(=\dfrac{2}{1}\cdot\dfrac{3}{2}\cdot...\cdot\dfrac{2020}{2019}\cdot\dfrac{2}{3}\cdot\dfrac{3}{4}\cdot...\cdot\dfrac{2020}{2021}\)
\(=2020\cdot\dfrac{2}{2021}=\dfrac{4040}{2021}\)
`(6^10:6^8):{780:[87.5-(125+5.7^2)+13.5]}`
`=6^2:[780:(435-49.5-125+65)]`
`=36:[780:(435-245-125+65)]`
`=36:(780:130)`
`=36:6`
`=6`
\(65.59+65.42-13.5=\left(65.59\right)+\left(65.42\right)-\left(13.5\right)=3835+2730-65=6565-65=6500\)