\(\left(2\dfrac{1}{3}+3\dfrac{1}{2}\right):\left(-4\dfrac{1}{6}+3\dfrac{1}{7}\right)+7\dfrac{1}{2}\)

\(=\left(\dfrac{7}{3}+\dfrac{7}{2}\right):\left(-\dfrac{25}{6}+\dfrac{22}{7}\right)+\dfrac{15}{2}\)

\(=\left(\dfrac{14+21}{6}\right):\left(\dfrac{-175+132}{42}\right)+\dfrac{15}{2}\)

\(=\dfrac{35}{6}:-\dfrac{43}{42}+\dfrac{15}{2}\)

\(=-\dfrac{245}{43}+\dfrac{15}{2}\)

\(=\dfrac{155}{86}\)

\(\left(2\dfrac{1}{3}+3\dfrac{1}{2}\right):\left(-4\dfrac{1}{6}+3\dfrac{1}{7}\right)+7\dfrac{1}{2}\)

\(=\left(\dfrac{7}{3}+\dfrac{7}{2}\right):\left(-\dfrac{23}{6}+\dfrac{22}{7}\right)+\dfrac{15}{2}\)

\(=\dfrac{35}{6}:\left(-\dfrac{29}{42}\right)+\dfrac{15}{2}\)

\(=-\dfrac{245}{29}+\dfrac{15}{2}\)

\(=-\dfrac{55}{58}\)

124 + (2012 - 2 . x) = 300

(2012 - 2 . x) = 300 - 124

(2012 - 2 . x) = 176

2 . x = 2012 - 176

2 . x = 1836

x = 1836 : 2

x = 918.

918

1538

1538

Nửa chu vi hình chữ nhật là :

           0,8 : 2 = 0,4 [ km ]

Ta có sơ đồ :

 Chiều rộng : 3 phần

 Chiều dài : 5 phần

                                            Giải

Chiều dài khu đất đó là :

          0,4 : [ 3 + 5 ] x 5 = 0,25 [ km ]

Chiều rộng khu đất đó là :

          0,4 - 0,25 = 0,15 [ km ]

Diện tích khu đất đó là :

          0,25 x 0,15 = 0,0375 [ km 2 ] 

                                Đ/S : 0,0375 km2

150 000m2

ĐKXĐ: \(x\ge-\dfrac{9}{2};x\ne0\)

\(\dfrac{2x^2}{\left(3-\sqrt{9+2x}\right)^2}=x+9\)

\(\Rightarrow\dfrac{2x^2\left(3+\sqrt{9+2x}\right)^2}{\left(3-\sqrt{9+2x}\right)^2\left(3+\sqrt{9+2x}\right)^2}=x+9\)

\(\Rightarrow\dfrac{2x^2\left(3+\sqrt{9+2x}\right)^2}{4x^2}=x+9\)

\(\Rightarrow\left(3+\sqrt{9+2x}\right)^2=2x+18\)

Đặt \(\sqrt{2x+9}=t\ge0;t\ne3\)

\(\Rightarrow\left(3+t\right)^2=t^2+9\Rightarrow t=0\)

\(\Rightarrow\sqrt{2x+9}=0\Rightarrow x=-\dfrac{9}{2}\)

con 11 tuổi

mẹ 43 tuổi

mẹ 43 tuổi , con 16 tuổi

`10+10+3-5+8`

`=20+3-5+8`

`=24-5+8`

`=18+8`

`=26`

10+10+3-5+8 = 20+3-5+8

                      = 18+8

                      = 26

úi, sorry, mk nhàm dấu ạ

\(A=1.2.3+2.3.4+3.4.5+...+99.100.101\)

\(\Rightarrow4A=1.2.3.4+2.3.4.4+99.100.101.4\)

\(\Rightarrow4A=1.2.3.\left(4-0\right)+2.3.4.\left(5-1\right)+...+99.100.101.\left(102-98\right)\)

\(\Rightarrow4A=\left(1.2.3.4+2.3.4.5+...+99.100+101.102\right)-\left(0.1.2.3+1.2.3.4+...+98.99.100.101\right)\)

\(\Rightarrow4A=99.100.101.102-0.1.2.3\)

\(\Rightarrow A=\dfrac{99.100.101.102-0.1.2.3}{4}\)

\(B=1.3.5+3.5.7+5.7.9+...+95.97.99\)

\(\Rightarrow8B=1.3.5.8+3.5.7.8+5.7.9.8+...+95.97.99.8\)

\(\Rightarrow8B=1.3.5.\left(7+1\right)+3.5.7.\left(9-1\right)+5.7.9.\left(11-3\right)+...+95.97.99.\left(101-93\right)\)

\(\Rightarrow8B=1.3.5.7+1.1.3.5+3.5.7.9-1.3.5.7+5.7.9.11-3.5.7.9+...+95.97.99.101-93.95.97.99\)

\(\Rightarrow8B=1.1.3.5+95.97.99.101\)

\(\Rightarrow B=\dfrac{1.1.3.5+95.97.99.101}{8}\)

B= 912720

`27 . 64 + 27 .33 + 3 . 27`

`=27 . (64 + 33 + 3)`

`=27. 100`

`=2700`

\(27.64+27.33+3.27\)

\(=27.\left(64+33+3\right)\)

\(=27.100\)

\(=2700\)