\(x:2+250.4=55.61+69.55-45.37-93.45\)

\(\Leftrightarrow x:2+1000=55\left(61+69\right)-45\left(37+93\right)\)

\(\Leftrightarrow x:2+1000=55.130-45.130\)

\(\Leftrightarrow x:2+1000=130\left(55-45\right)\)

\(\Leftrightarrow x:2+1000=130.10\)

\(\Leftrightarrow x:2+1000=1300\)

\(\Leftrightarrow x:2=1300-1000=300\)

\(\Leftrightarrow x=300.2=600\)

Vậy \(x=600\)

X:2+250*4=55*61+69*55-45*37-93*45

X:2+250*4=(55*61+69*55)-(45*37+93*45)

X:2+1000=55*(61+69)-45*(37+93)

X:2+1000=55*130-45*130

X:2+1000=(55-45)*130

X:2+1000=10*130

X:2+1000=1300

X:2=1300-1000

X:2=300

X=300*2

X=600

Vậy X = 600

1)

\(45\left(13+78\right)+9\left(87+22\right)5\)

\(=45\left(13+78\right)+45\left(87+22\right)\)

\(=45\left(13+78+87+22\right)\)

\(=45\left[\left(87+13\right)+\left(78+22\right)\right]\)

\(=45\left[100+100\right]\)

\(=45.200\)

\(=9000\)

2)

\(43+37+93.43+57.61+69.57\)

\(=43\left(37+93\right)+57.\left(61+69\right)\)

\(=43.130+57.130\)

\(=130\left(43+57\right)\)

\(=130.100\)

=13000

a) 28 + 55 = 83

45 + 49 = 94

37 + 53 = 90

b) 61 - 18 = 43

53 - 26 = 27

92 - 84 = 8

\(\begin{array}{*{20}{c}}{a)\,\,}\\{}\\{}\end{array}\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{28}\\{55}\end{array}}\\\hline{\,\,\,\,83}\end{array}\)                    \(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{45}\\{49}\end{array}}\\\hline{\,\,\,\,94}\end{array}\)                            \(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{37}\\{53}\end{array}}\\\hline{\,\,\,\,90}\end{array}\)

\(\begin{array}{*{20}{c}}{b)\,\,}\\{}\\{}\end{array}\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{61}\\{18}\end{array}}\\\hline{\,\,\,43}\end{array}\)                    \(\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{53}\\{26}\end{array}}\\\hline{\,\,\,27}\end{array}\)                           \(\begin{array}{*{20}{c}}{ - \begin{array}{*{20}{c}}{92}\\{84}\end{array}}\\\hline{\,\,\,08}\end{array}\)

\(a,=\left(93-7\right)\left(93+7\right)=100\cdot86=8600\\ b,=\left(45+55\right)^2=100^2=10000\)

\(\dfrac{51}{53}+\dfrac{55}{57}+\dfrac{61}{63}+\dfrac{69}{71}+\dfrac{79}{81}+\dfrac{91}{93}\) 

\(=\left(\dfrac{52}{53}-\dfrac{1}{53}\right)+\left(\dfrac{56}{57}-\dfrac{1}{57}\right)+\left(\dfrac{62}{63}-\dfrac{1}{63}\right)+\left(\dfrac{70}{71}-\dfrac{1}{71}\right)+\left(\dfrac{80}{81}-\dfrac{1}{81}\right)+\left(\dfrac{92}{93}-\dfrac{1}{93}\right)\)

\(=\left(1-\dfrac{1}{53}-\dfrac{1}{53}\right)+\left(1-\dfrac{1}{57}-\dfrac{1}{57}\right)+\left(1-\dfrac{1}{63}-\dfrac{1}{63}\right)+\left(1-\dfrac{1}{71}-\dfrac{1}{71}\right)+\left(1-\dfrac{1}{81}-\dfrac{1}{81}\right)+\left(1-\dfrac{1}{93}-\dfrac{1}{93}\right)\)

\(=\left(1-0\right)+\left(1-0\right)+\left(1-0\right)+\left(1-0\right)+\left(1-0\right)+\left(1-0\right)\) 

\(=1+1+1+1+1+1\) 

\(=6\)

=(45+55)+(39+61)+89

=100 + 100 + 89

= 200 + 8 9 

= 289

39 + 45 + 61 + 55 + 89 = 289

yick nha

39+45+61+55+89

=(39+61)+(45+55)+89

=100+100+89

=200+89

=289

câu này hỏi gì, là sao vậy??

Mình không hiểu gì hết

ko hỉu

Tính nhanh :

a)8 x 45 + 55 x 8 

= 8x(45+55)

= 8x100

=800

28 x 69 + 31 x 28 

= 28x(69+31)

= 28x100

=2800

Ta có :

8 x 45 + 55 x 8 

= 8 x ( 45 + 55 )

= 8 x 100 

= 800

28 x 69 + 31 x 28 

= 28 x ( 69 + 31 )

= 28 x 100 

= 2800

mik tl trước mak 

a, (57-7250) + ( 605-53) = 57 - 7250 + 605 - 53 = - 6641

b, (55 + 45 + 15) - (15-55+45) = 55 + 45 + 15 - 15 + 55 - 45 = 110

c, (15 + 37) + (52-37-17) = 15+37+52-37-17= 50

Xong rồi đó k cho mk nha bn