10/40 = 1/4

x/2 = 1/4 => x.4 = 1.2 => x = 1.2/4 = 0,5

5/y = 1/4 => y.1 = 5.4 => y = 20

z/8 = 1/4 => z.4 = 8.1 => z = 8.1/4 = 2

\(ĐK:2\le x\le10\)

\(PT\Leftrightarrow\left(\sqrt{x-2}-2\right)+\left(\sqrt{10-x}-2\right)=x^2-12x+36\\ \Leftrightarrow\dfrac{x-6}{\sqrt{x-2}+2}+\dfrac{6-x}{\sqrt{10-x}+2}-\left(x-6\right)^2=0\\ \Leftrightarrow\left(x-6\right)\left(\dfrac{1}{\sqrt{x-2}+2}-\dfrac{1}{\sqrt{10-x}+2}-x+6\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=6\left(tm\right)\\\dfrac{1}{\sqrt{x-2}+2}-\dfrac{1}{\sqrt{10-x}+2}-x+6=0\left(1\right)\end{matrix}\right.\)

Với \(x\le10\Leftrightarrow\left(1\right)\le\dfrac{1}{2\sqrt{2}+2}-\dfrac{1}{2}-10+6< 0\Leftrightarrow x\in\varnothing\)

Vậy \(x=6\)

(-15)\(x\) = - 45

       \(x\)  = - 45 : (-15)

      \(x\)  = 3

Vậy \(x=3\)

(-15)\(x\) = 10.(-40).(-5)

    -15\(x\)  =  -400.(-5)

   -15\(x\)   = 2000

    \(x\)   = 2000 : (-15)

    \(x\)  = - \(\dfrac{400}{3}\)

Vậy \(x=-\dfrac{400}{3}\) 

(+2).\(x\)  = - 16

      \(x\)   = -16 : (2)

      \(x\)  = - 8

Vậy \(x=-8\)

a)

\(P=\dfrac{x^{10}-x^8+x^6-x^4+x^2-1}{x^4-1}\)

\(=\dfrac{x^8\left(x^2-1\right)+x^4\left(x^2-1\right)+\left(x^2-1\right)}{\left(x^2-1\right)\left(x^2+1\right)}\)

\(=\dfrac{\left(x^2-1\right)\left(x^8+x^4+1\right)}{\left(x^2-1\right)\left(x^2+1\right)}\)

\(=\dfrac{x^8+x^4+1}{x^2+1}\)

b)

\(Q=\dfrac{x^{40}+x^{30}+x^{20}+x^{10}+1}{x^{45}+x^{40}+x^{35}+...+x^{10}+x^5+1}\)

\(=\dfrac{x^{40}+x^{30}+x^{20}+x^{10}+1}{\left(x^{45}+x^{35}+...+x^5\right)+\left(x^{40}+x^{30}+...+1\right)}\)

\(=\dfrac{x^{40}+x^{30}+x^{20}+x^{10}+1}{x^5\left(x^{40}+x^{30}+...+1\right)+\left(x^{40}+x^{30}+...+1\right)}\)

\(=\dfrac{x^{40}+x^{30}+x^{20}+x^{10}+1}{\left(x^{40}+x^{30}+...+1\right)\left(x^5+1\right)}\)

\(=\dfrac{1}{\left(x^5+1\right)}\)

bạn làm đúng rồi đó

bạn làm rất tốt .

thiếu Vậy ....

\(a,\left(2\times x-40\right):10=-55\)

\(2\times x-40=-55\times10\)

\(2\times x-40=-550\)

\(2\times x=-550+40\)

\(2\times x=-510\)

\(x=-510:2\)

\(\Rightarrow x=-255\)

\(b,\left(2\times x+15\right):5=-40\)

\(2\times x+15=-40\times5\)

\(2\times x+15=-200\)

\(2\times x=-200-15\)

\(2\times x=-215\)

\(x=-215:2\)

\(\Rightarrow x=-\dfrac{215}{2}\)

\(c,\left(2\times x-72\right):8=25\)

\(2\times x-72=25\times8\)

\(2\times x-72=200\)

\(2\times x=200+72\)

\(2\times x=272\)

\(x=272:2\)

\(\Rightarrow x=136\)

GIÚP MÌNH VỚI

a. ( 2.x - 40 ) ÷ 10 = -55 

                 2.x - 40  = (-55) × 10 

                 2.x - 40  = -550 

                           2.x = (-550) + 40

                           2.x = -510 

                               x = (-510) ÷ 2 

                               x = -255 

b. ( 2.x + 15 ) ÷ 5 = -40 

                2.x + 15 =  (-40) × 5 

                 2.x + 15 = -200 

                          2.x = (-200 ) - 15 

                          2.x = -215 

                              x = (-215) ÷ 2 

                              x = -107,5 

c. ( 2.x - 72 ) ÷ 8 = 25 

                2.x - 72 = 25 × 8 

                2.x - 72 = 200 

                       2.x  = 200 + 72 

                        2.x = 272 

                            x = 272 ÷ 2 

                            x = 136