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Mathematics

Solve :

3x+2y=10\dfrac{3}{x} + \dfrac{2}{y} = 10

9x7y=10.5\dfrac{9}{x} - \dfrac{7}{y} = 10.5

Linear Equations

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Answer

Given, equations :

3x+2y=10\Rightarrow \dfrac{3}{x} + \dfrac{2}{y} = 10 …………(1)

9x7y=10.5\Rightarrow \dfrac{9}{x} - \dfrac{7}{y} = 10.5 ……….(2)

Multiplying equation (1) by 3, we get :

3(3x+2y)=3×109x+6y=30……….(3)\Rightarrow 3\Big(\dfrac{3}{x} + \dfrac{2}{y}\Big) = 3 \times 10 \\[1em] \Rightarrow \dfrac{9}{x} + \dfrac{6}{y} = 30 ……….(3)

Subtracting equation (2) from (3), we get :

(9x+6y)(9x7y)=3010.59x9x+6y+7y=19.513y=19.5y=1319.5y=11.5=23.\Rightarrow \Big(\dfrac{9}{x} + \dfrac{6}{y}\Big) - \Big(\dfrac{9}{x} - \dfrac{7}{y}\Big) = 30 - 10.5 \\[1em] \Rightarrow \dfrac{9}{x} - \dfrac{9}{x} + \dfrac{6}{y} + \dfrac{7}{y} = 19.5 \\[1em] \Rightarrow \dfrac{13}{y} = 19.5 \\[1em] \Rightarrow y = \dfrac{13}{19.5} \\[1em] \Rightarrow y = \dfrac{1}{1.5} = \dfrac{2}{3}.

Substituting value of y in equation (1), we get :

3x+223=103x+62=103x+3=103x=7x=37.\Rightarrow \dfrac{3}{x} + \dfrac{2}{\dfrac{2}{3}} = 10 \\[1em] \Rightarrow \dfrac{3}{x} + \dfrac{6}{2} = 10 \\[1em] \Rightarrow \dfrac{3}{x} + 3 = 10 \\[1em] \Rightarrow \dfrac{3}{x} = 7 \\[1em] \Rightarrow x = \dfrac{3}{7}.

Hence, x = 37 and y=23\dfrac{3}{7} \text{ and } y = \dfrac{2}{3}.

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