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(45+75)*66+(75+45)*34
=(45+75)*(66+34)
=120*100
=12000
11+22+33+44+55+66+77+88+99:11
=11+22+33+44+55+66+77+88+9
=(11+9)+(22+88)+(33+77)+(44+66)+55
=20+110*3+55
=20+330+55
=405
Ta có :
a, (45 + 75) x 66 + (75 + 45) x 34
= (45 + 75) x (66 + 34)
= 120 x 100
= 12000
11 + 22 + 33 + 44 + 55 + 66 + 77 + 88 + 99 : 11
= 33 + 77 + 121 + 165 + 9
= 405
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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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4a) \(\frac{x}{36}=\frac{3}{4}\)
\(\Rightarrow\frac{x}{36}=\frac{27}{36}\)
\(\Rightarrow x=27\)
4b) 33 + x = 71 - 26
33 + x = 45
x = 45 - 33
x = 12
4c) x * (3,5 + 1,5) = 10
x * 5 = 10
x = 10 ; 5 = 2
4,
\(a,\frac{x}{36}=\frac{24}{32}\)
\(=>\frac{x}{36}=\frac{3}{4}=\frac{27}{36}\)
\(=>x=27\)
\(b,71-\left(33+x\right)=26\)
\(=>-\left(33+x\right)=26-71=-45\)
\(=>33+x=45\)
\(=>x=12\)
\(c,3,5\cdot x+1,5\cdot x=10\)
\(>x\cdot\left(3,5+1,5\right)=10\)
\(=>x\cdot5=10\)
\(=>x=2\)
. là nhân nha
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Bài 1:
\(A=\frac{1}{\left(1+2\right)}+\frac{1}{\left(1+2+3\right)}+\frac{1}{\left(1+2+3+4\right)}\)\(+\frac{1}{\left(1+2+3+4+5\right)}+...+\)\(\frac{1}{\left(1+2+3+...+10\right)}\)
\(A=\frac{1}{3}+\frac{1}{6}+....+\frac{1}{55}\)
\(A=2\left(\frac{1}{6}+\frac{1}{12}+....+\frac{1}{110}\right)\)
\(A=2\left(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{10.11}\right)\)
\(A=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{10}-\frac{1}{11}\right)\)
\(A=2.\left(\frac{1}{2}-\frac{1}{11}\right)\)
\(A=\frac{9}{11}\)
Bài 2 :
2) Tử số = 11 x 13 x 15 + 3 x 3 x 3 x 11 x 13 x 15 + 5 x 5 x 5 x 11 x 13 x 15 + 9 x 9 x 9 x 11 x 13 x 15
= (1 + 3 x 3 x 3 + 5 x 5 x 5 + 9 x 9 x9) x 11 x 13 x 15 = (1+27+125+ 729) x 11 x 13 x 15
Mẫu số = 11 x 13 x 17 + 3 x 3 x 3 x 13 x 15 x 19 + 5 x 5 x 5 x 13 x 15 x 17 + 9 x 9 x 9 x 13 x 15 x 17 lớn hơn 11 x 13 x 15 + 3 x 3 x 3 x 13 x 15 x 17 + 5 x 5 x 5 x 13 x 15 x 17 + 9 x 9 x 9 x 13 x 15 x 17
= (1 + 3 x 3 x 3 + 5 x 5 x 5 + 9 x 9 x9) 13 x 15 x 17 = (1+27+125+729) x 13 x 15 x 17
\(\Rightarrow A< \frac{\left(1+27+125+729\right)\times11\times13\times15}{\left(1+27+125+729\right)\times13\times15\times17}\)
\(=\frac{11}{17}\)
\(=\frac{1111}{1717}=B\)
Vậy \(A=B\)
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a) 6625 + 3525 - 25 d) 35 x 34 + 35 x 86 + 65 x 75 + 65 x 45
= 6625 + ( 3525 -25) = 35 x (34 + 86 ) + 65 x (75 + 45 )
= 6625 + 3500 = 35 x 120 + 65 x 120
= 10 125 = 120 x ( 35 + 65 )
= 120 x 100
= 12 000
a) 6625 + 3525 - 25
=10125
b) 58 x 42 + 32 x 8 + 5 x 16
= 2436 + 256 + 80
= 2772
c) (4243 + 4357 + 43) - 360 : 4
= 8643 - 360: 4
= 8642 - 90
= 8552
d) 35 x 34 + 35 x 86 + 65 x 75 + 65 x 45
= (34 +86) x 35 + (75 + 45) x 65
= 120 x 35 + 120 x 65
= 120 x (35+65)
= 120 x 100
= 12000
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1)\(A=\frac{1}{3}+\frac{1}{6}+...+\frac{1}{55}=2\left(\frac{1}{6}+\frac{1}{12}+...+\frac{1}{110}\right)=2\left(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{10.11}\right)=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{10}-\frac{1}{11}\right)=2.\left(\frac{1}{2}-\frac{1}{11}\right)=\frac{9}{11}\)
2) Tử số = 11 x 13 x 15 + 3 x 3 x 3 x 11 x 13 x 15 + 5 x 5 x 5 x 11 x 13 x 15 + 9 x 9 x 9 x 11 x 13 x 15
= (1 + 3 x 3 x 3 + 5 x 5 x 5 + 9 x 9 x9) x 11 x 13 x 15 = (1+27+125+ 729) x 11 x 13 x 15
Mẫu số = 11 x 13 x 17 + 3 x 3 x 3 x 13 x 15 x 19 + 5 x 5 x 5 x 13 x 15 x 17 + 9 x 9 x 9 x 13 x 15 x 17
lớn hơn 11 x 13 x 15 + 3 x 3 x 3 x 13 x 15 x 17 + 5 x 5 x 5 x 13 x 15 x 17 + 9 x 9 x 9 x 13 x 15 x 17
= (1 + 3 x 3 x 3 + 5 x 5 x 5 + 9 x 9 x9) 13 x 15 x 17 = (1+27+125+729) x 13 x 15 x 17
=> \(A
mik chỉ nêu cách lm
a) ((5*(191-109)))+((624-296)/4))
b)100*66+100*35
=100*(66+35)=
( 191 x 5 - 109 x 5 ) + ( 624 : 4 - 296 : 4 )
= [ ( 191 - 109 ) x 5 ] + [ ( 624 - 296 ) : 4 ]
= 82 x 5 + 82
= 82 x ( 5 + 1 )
= 82 x 6
= 492
( 45 + 75 ) x 66 + ( 75 + 45 ) x 35
= ( 45 + 75 ) x ( 66 + 35 )
= 120 x 101
= 12120
hok tốt