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Mathematics

The solution of the simultaneous equations 2x+1y=02x + \dfrac{1}{y} = 0 and 3x+12y=23x + \dfrac{1}{2y} = -2 is :

  1. x = 1, y = 12\dfrac{1}{2}

  2. x = 1, y = 12-\dfrac{1}{2}

  3. x = -1, y = 12\dfrac{1}{2}

  4. x = -1, y = 12-\dfrac12

Linear Equations

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Answer

Given,

Equations: 2x+1y=02x + \dfrac{1}{y} = 0 and 3x+12y=23x + \dfrac{1}{2y} = -2

Solving equation 1,

2x+1y=02x + \dfrac{1}{y} = 0

⇒ 2x = 1y-\dfrac{1}{y}

⇒ x = 12y\dfrac{-1}{2y}     …….(1)

Substituting value of x from equation (1) in 3x+12y=23x + \dfrac{1}{2y} = -2, we get :

3(12y)+12y=232y+12y=222y=2y=22×2y=12.\Rightarrow 3\Big(\dfrac{-1}{2y}\Big) + \dfrac{1}{2y} = -2 \\[1em] \Rightarrow \dfrac{-3}{2y} + \dfrac{1}{2y} = -2 \\[1em] \Rightarrow \dfrac{-2}{2y} = -2 \\[1em] \Rightarrow y = \dfrac{-2}{-2 \times 2} \\[1em] \Rightarrow y = \dfrac{1}{2}.

Substituting y = 12\dfrac{1}{2} in equation (1), we get :

x=12yx=12(12)x=1.\Rightarrow x = \dfrac{-1}{2y} \\[1em] \Rightarrow x = \dfrac{-1}{2\Big(\dfrac{1}{2}\Big)} \\[1em] \Rightarrow x = -1.

Hence, option 3 is the correct option.

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