Y÷1/2 + Y÷1/3 + Y÷1/4 +Y = 450 <=>Y×2 + Y×3 + Y+4 + Y = 450

<=> Y×(2+3+4+1) = 450

<=> 10Y = 450

<=> Y= 450÷10

<=> Y= 45

a) \(=\left(278+622\right)+\left(809-209\right)=900+600=1500\)

b) \(=64.57+64.43-2300=64\left(57+43\right)-2300=54.100-2300=5400-2300=3100\)

a) 278+809+622-209
  = (278+622)+(809-209)
  =       900    +    600
  =              1500
b) 64.57+64.43-2300
  = 64(57+43)-2300
  = 64.100-2300
  = 6400-2300=4100
c) 24.5-[131-(13-4)2]
  = 24.5-(131-9.2)
  = 120-113= 7

\(3\times5\times622\times52452524\\ =\left(3\times5\right)\times\left(622\times52452524\right)\\ =15\times32625469928\\ =489382048920\)

Cái này không học cái này đâu <2

3×5×622×52452524

=(3×5)×(622×52452524)

=15×32625469928

=489382048920

Tớ gửi ạ!

ĐÁP ÁN B

Không báo cáo nữa nhé !

Ơ thự nhiên không có ai trả lời thế nhỉ.

bạn hỏi khó....

`a,`

`2,9,8,2,0,3,5,6`

`4,7,0,3,6,2,2`

`b, 620 403 500; 6;2;0;4;0;3;5;0;0`

`5;0;2;8;7;0;0;3;1`

\(\dfrac{450}{x+30}-\dfrac{450}{x}=4\left(đk:x\ne0,x\ne-30\right)\)

\(\Leftrightarrow\dfrac{450x-450x-13500}{x\left(x+30\right)}=4\)

\(\Leftrightarrow\dfrac{-13500}{x\left(x+30\right)}=4\)

\(\Leftrightarrow4x^2+120x=-13500\)

\(\Leftrightarrow4\left(x+15\right)^2=-12600\)

\(\Leftrightarrow\left(x+15\right)^2=-3150\)(vô lý)

Vậy \(x\in\varnothing\)

\(\dfrac{450}{x+30}-\dfrac{450}{x}=4\)

<=> \(\dfrac{450x}{x\left(x+30\right)}-\dfrac{450\left(x+30\right)}{x\left(x+30\right)}=\dfrac{4x\left(x+30\right)}{x\left(x+30\right)}\)

<=> 450x - 450(x + 30) = 4x(x + 30)

<=> 450x - 450x - 480 = 4x² + 120x

<=> 4x² - 120x - 480 = 0

<=> x = 33, 57

Ta có: \(\dfrac{450}{x+30}-\dfrac{450}{x}=4\)

\(\Leftrightarrow4x\left(x+30\right)=450x-450\left(x+30\right)\)

\(\Leftrightarrow4x^2+120x+13500=0\)(vô lý)

\(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{460}\\{231}\end{array}}\\\hline{\,\,\,691}\end{array}\)                                    \(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{375}\\{622}\end{array}}\\\hline{\,\,\,997}\end{array}\)

\(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{800}\\{\,\,37}\end{array}}\\\hline{\,\,\,837}\end{array}\)                                    \(\begin{array}{*{20}{c}}{ + \begin{array}{*{20}{c}}{923}\\{\,\,\,\,6}\end{array}}\\\hline{\,\,\,929}\end{array}\)

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