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1: =66+34-73-27+99=99
2: =54-45+30-54-30+5=-40
3: =42-56+33-33+56-42=0
4: =50-47-50+18+47-18=0
5: =10-28+30-4=2-4+10=12-4=8
\(\text{1.-(-66)+34+(-73)-27+99}.\)
\(=66+34-73-27+99=100-100+99=-99.\)
\(\text{2.54-(45-30+54)-30+5}.\)
\(54-45+30-54-30+5=\left(54-54\right)+\left(-45+5\right)+\left(30-30\right)=-40.\)
\(\text{3.42-56+33-(33-56+42)}.\)
\(=42-56+33-33+56-42=\left(42-42\right)+\left(-56+56\right)+\left(33-33\right)=0.\)
\(\text{4.50-(47+50-18)+(47-18)}.\)
\(=50-47-50+18+47-18=\left(50-50\right)+\left(-47+47\right)+\left(18-18\right)=0.\)
\(\text{5.10-(28-30+4)}.\)
\(=10-28+30-4=10+30-20-8-4=20-12=8.\)
\(\text{6.-(-73)+(44-94+27)+94}.\)
\(=73+44-94+27+94=\left(73+27\right)+\left(-94+94\right)+44=100+44=144.\)
a) \(48.19+48.15+134.52\)
\(=48\left(19+15\right)+6968\)
\(=48.34+6968\)
\(=1632+6968\)
\(=8600.\)
b) \(27.121-87.27+73.34\)
\(=27\left(121-87\right)+73.34\)
\(=27.34+73.34\)
\(=34\left(27+73\right)\)
\(=34.100\)
\(=3400.\)
c) \(125.98-125.46-52-25\)
\(=125\left(98-46\right)-52-25\)
\(=125.52-52-25\)
\(=52\left(125-1\right)-25\)
\(=52.124-25\)
\(=6448-25\)
\(=6423.\)
d) \(136.23+136.17-40.36\)
\(=136\left(23+17\right)-40.36\)
\(=136.40-40.36\)
\(=40\left(136-36\right)\)
\(=40.100\)
\(=4000.\)
e) \(66.25+5.66+66.14+33.94\)
\(=33\left(2.50+5.2+14.2+94\right)\)
\(=33\left(50+10+28+94\right)\)
\(=33.182\)
\(=6006.\)
a , 27 . ( 58 - 43 ) + 43 . ( 27 + 58 ) b . 66 . ( 34 - 75 ) - 34 . ( 66 + 75 )
= 27 . 10 + 43 . 85 = 66 . ( 34 - 75 ) + ( -34 ) . ( 66 + 75 )
= 270 + 3755 = [ 66 . 75 + 66 + 75 ] . 34 . ( - 34 )
= 4025 0
k và kb nếu có thể
27.121-87.27+73.34
= 27( 121-87) +73.34
= 27. 34 +73.34
= 34( 27+73 )
= 34. 100
= 3400
27. 121 - 87. 27+ 73. 34
= 27 . (121 - 87 ) + 73. 34
= 27 . 34 + 73 .34
= 34 . ( 27 + 73 )
= 34 . 100 = 3400
a) 48.19 + 48.115 + 134.52
= 48.(19+115)+134.52
= 48.134+134.52
= 134.(48+52)
= 134.100
= 13400
$b.27.121+87.27+73.3= 27.(121+87)+73.34b) 27.121 + 87.27 + 73.34
= 27.(121+87)+73.34
= 27.208 + 73.34
= 5616 + 2482
= 8098
\(2+4+6+....+2n=90\Leftrightarrow2\left(1+2+3+...+n\right)=90\Leftrightarrow1+2+3+...+n=45\Leftrightarrow\frac{n\left(n+1\right)}{2}=45\Leftrightarrow n\left(n+1\right)=90=9.10\Rightarrow n=9\)
\(a+b=8\Rightarrow a\in\left\{1;2;3;4;....;8\right\}\Rightarrow A=\left\{17;26;35;44;53;62;71;80\right\}\)
\(ab.101=ab.100+ab=ab00+ab=abab\)
Bài 1.
\( a)71 - \left( {33 + x} \right) = 26\\ \Leftrightarrow 71 - 33 - x = 26\\ \Leftrightarrow 38 - x = 26\\ \Leftrightarrow - x = 26 - 38\\ \Leftrightarrow - x = - 12\\ \Leftrightarrow x = 12\\ b)\left( {x + 73} \right) - 26 = 76\\ \Leftrightarrow x + 73 - 26 = 76\\ \Leftrightarrow x + 47 = 76\\ \Leftrightarrow x = 76 - 47\\ \Leftrightarrow x = 29\\ c)140:\left( {x - 8} \right) = 7\\ \Leftrightarrow x - 8 = 140:7\\ \Leftrightarrow x - 8 = 20\\ \Leftrightarrow x = 20 + 8\\ \Leftrightarrow x = 28\\ d)6x + 4x = 2010\\ \Leftrightarrow 10x = 2010\\ \Leftrightarrow x = \dfrac{{2010}}{{10}}\\ \Leftrightarrow x = 201 \)
= 66 + 34 -73 - 27 + 99
= 100 - (73+27) + 99
=100 - 100 + 99 = 99
Trl : 99
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