\(\dfrac{1}{1\cdot2}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{49}-\dfrac{1}{50}\)

= \(1-\dfrac{1}{2}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{49}-\dfrac{1}{50}\)

= \(\left(1+\dfrac{1}{3}+...+\dfrac{1}{49}\right)-\left(\dfrac{1}{2}+\dfrac{1}{4}+...+\dfrac{1}{50}\right)\)

= \(\left(1+\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+...+\dfrac{1}{49}+\dfrac{1}{50}\right)-2\left(\dfrac{1}{2}+\dfrac{1}{4}+...+\dfrac{1}{50}\right)\) 

= \(\left(1+\dfrac{1}{2}+\dfrac{1}{3}+...+\dfrac{1}{50}\right)-\left(1+\dfrac{1}{2}+...+\dfrac{1}{25}\right)\)

= \(\dfrac{1}{26}+\dfrac{1}{27}+...+\dfrac{1}{50}\)

Vậy \(\dfrac{1}{26}+\dfrac{1}{27}+...+\dfrac{1}{50}\) = \(\dfrac{1}{26}+\dfrac{1}{27}+...+\dfrac{1}{50}\) hay

\(\dfrac{1}{1\cdot2}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{49}-\dfrac{1}{50}\) = \(\dfrac{1}{26}+\dfrac{1}{27}+...+\dfrac{1}{50}\)

     ( x - 2/2 )^2 = 1/4

=> ( x - 2/2 )^2 = 1/2^2

=>   x -2/2 = 1/2

=>  x  = 1/2 + 2/2

=>  x  =    3/2

Vậy x = 3/2

`(-3737)/4141 = (-3737:101)/(4141:101) = -37/41`

Đổi 216l = 216 dm³

Gọi độ dài cạnh của bể cá là x

Ta có 216 = x . x . x

          6³ = x³

Vậy độ dài cạnh của bể cá là 6dm

Diện tích xung quanh của bể cá là 6 . 6 . 4 = 144 ( dm² )

xy-x+2y-1=0

<=> x(y-1) +2y -2 -1 = -2

<=> (x-2)(y-1)= -1

Có -1 = 1.(-1) = (-1).1

⇒ (x-2)(y-1)=-1

<=> (x-2)(y-1)=1 ⇒ x=2, y = 0 

       (x-2)(y-1)=1 ⇒ x=1, y= 1

Nhớ tick đúng nkeee :>>

\(a,2x=\dfrac{4^7}{4^3}=4^{7-3}=4^4\\ =>x=\dfrac{4^4}{2}=\dfrac{256}{2}=128\\ b,3^x=\dfrac{9^4}{81^3}=\dfrac{9^4}{9^{2.3}}\\ =>3^x=\dfrac{9^4}{9^6}=9^{-2}\\ =>3^x=3^{2.\left(-2\right)}=3^{-4}\\ =>x=-4\)