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45 x t = 35 x [ t + ( 40/60 ) ]
45 x t = 35 x ( t + 2/3 )
45 x t = 35 x t + 70/3
45 x t - 35 x t = 70/3
10 x t = 70/3
t = 70/3 : 10
t = 7/3
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71 * x - x = 365 - 3 * x
x * (71 - 1) = 365 - 3 * x
x * 70 = 365 - 3 * x
x * 70 + 3 * x = 365
x * 73 = 365
x = 5
Câu 2 đề thiếu nhá
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100%:x-50%:x+40%:x=18+30%:x
<=> (100% - 50% + 40%) : x = 18 + 30% : x
<=> 90% : x = 18 + 30% : x
=> 90% : x - 30% : x = 18
=> (90% - 30%) : x = 18
<=> x = 60% : 18
=> x = 1/30
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a)27*47+13*24+24*10*3
=27*47+13*24+24*30
=27*47+24*(13+30)
=27*47+24*43
=2301
b)
55-50+45-40+35-30+25-20+15-10+5
=(55-50)+(45-40)+(35-30)+(25-20)+(15-10)+5
=5+5+5+5+5+5
=30
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(82 - 5.x) : 13 - 4 = 0
(82 - 5.x) : 13 = 0 + 4
(82 - 5.x) : 13 = 4
(82 - 5.x) = 4 . 13
(82 - 5.x) = 52
5.x = 82 - 52
5.x = 30
x = 30 : 5 = 6
(32 . 45) : 2 = (x + 70) : 14 - 40
720 = (x + 70) : 14 - 40
(x + 70) : 14 = 720 + 40
(x + 70) : 14 = 760
(x + 70) = 760 . 14
(x + 70) = 10640
x = 10640 - 70
x = 10570
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35 . 34 + 35 . 38 + 65 . 75 + 65 . 45 + 35 . 34 =
= 35 . 34 + 35 . 38 + 35 . 34 + 65 . 75 + 65 . 45
= 35 . ( 34 + 38 + 34 ) + 65 . ( 75 + 45 )
= 35 . 110 + 65 . 110
= 110 . ( 35 + 65 )
= 110 . 100
= 11000
Hok tốt!!!!!!!!!!!!!
a) Tính bằng cách hợp lí nhất :
35 . 34 + 35 . 38 + 65 . 75 + 65 . 45 + 35 . 34
= 35 . 34 + 35 . 38 + 35 . 34 + 65 . 75 + 65 . 45
= 35 . ( 34 + 38 + 34 ) + 65 . ( 75 + 45 )
= 35 . 106 + 65 . 120
= 3710 + 7800
= 11510
3 . 25 . 8 + 4 . 37 . 6 + 2 . 38 . 12
= 3 . 8 . 25 + 4 . 6 . 37 + 2 . 12 . 38
= 24 . 25 + 24 . 37 + 24 . 38
= 24 . ( 25 + 37 + 38 )
= 24 . 100
= 2400
b) Tìm số tự nhiên x, biết :
( x - 5 ) ( x + 7 ) = 0
\(\Rightarrow\orbr{\begin{cases}x-5=0\\x+7=0\end{cases}\Rightarrow\orbr{\begin{cases}x=5\\x=-7\end{cases}}}.\)
Vậy .......
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