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Mathematics

Solution of equations 2x3y=13 and 3x+2y\dfrac{2}{x} - \dfrac{3}{y} = 13 \text{ and } \dfrac{3}{x} + \dfrac{2}{y} = 0 is :

  1. x=12,y=13x = \dfrac{1}{2}, y = \dfrac{1}{3}

  2. x=12,y=13x = -\dfrac{1}{2}, y = \dfrac{1}{3}

  3. x=12,y=13x = \dfrac{1}{2}, y = -\dfrac{1}{3}

  4. x=12,y=13x = -\dfrac{1}{2}, y = -\dfrac{1}{3}

Linear Equations

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Answer

Given, equations :

2x3y=13\dfrac{2}{x} - \dfrac{3}{y} = 13 …….(1)

3x+2y=0\dfrac{3}{x} + \dfrac{2}{y} = 0 ……..(2)

Multiplying equation (1) by 2, we get :

2(2x3y)=2×134x6y=26 …….(3)\Rightarrow 2\Big(\dfrac{2}{x} - \dfrac{3}{y}\Big) = 2 \times 13 \\[1em] \Rightarrow \dfrac{4}{x} - \dfrac{6}{y} = 26 \text{ …….(3)}

Multiplying equation (2) by 3, we get :

3(3x+2y)=3×09x+6y=0 …….(4)\Rightarrow 3\Big(\dfrac{3}{x} + \dfrac{2}{y}\Big) = 3 \times 0 \\[1em] \Rightarrow \dfrac{9}{x} + \dfrac{6}{y} = 0 \text{ …….(4)}

Adding equations (3) and (4), we get :

(4x6y)+(9x+6y)=26+04x+9x6y+6y=2613x=26x=1326=12.\Rightarrow \Big(\dfrac{4}{x} - \dfrac{6}{y}\Big) + \Big(\dfrac{9}{x} + \dfrac{6}{y}\Big) = 26 + 0 \\[1em] \Rightarrow \dfrac{4}{x} + \dfrac{9}{x} - \dfrac{6}{y} + \dfrac{6}{y} = 26 \\[1em] \Rightarrow \dfrac{13}{x} = 26 \\[1em] \Rightarrow x = \dfrac{13}{26} = \dfrac{1}{2}.

Substituting value of x in equation (2), we get :

312+2y=06+2y=02y=062y=6y=26=13.\Rightarrow \dfrac{3}{\dfrac{1}{2}} + \dfrac{2}{y} = 0 \\[1em] \Rightarrow 6 + \dfrac{2}{y} = 0 \\[1em] \Rightarrow \dfrac{2}{y} = 0 - 6 \\[1em] \Rightarrow \dfrac{2}{y} = -6 \\[1em] \Rightarrow y = \dfrac{2}{-6} = -\dfrac{1}{3}.

Hence, Option 3 is the correct option.

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