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Mathematics

Solve the following simultaneous equations:

2x+23y=16,  3x+2y=0\dfrac{2}{x} + \dfrac{2}{3y} = \dfrac{1}{6},\;\dfrac{3}{x} + \dfrac{2}{y} = 0

Linear Equations

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Answer

Given,

Equations:

2x+23y=16 ….(1) \dfrac{2}{x} + \dfrac{2}{3y} = \dfrac{1}{6} \text{ ….(1) },

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

Multiplying equation (1) by 3, we get:

3(2x+23y)=16×3(6x+2y)=12 ….(3) \Rightarrow 3\Big(\dfrac{2}{x} + \dfrac{2}{3y}\Big) = \dfrac{1}{6} \times 3 \\[1em] \Rightarrow \Big(\dfrac{6}{x} + \dfrac{2}{y}\Big) = \dfrac{1}{2} \text{ ….(3) }

Multiplying equation (2) by 2, we get:

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

Subtracting equation (3) from (4), we get:

(6x+4y)(6x+2y)=012(6x+4y6x2y)=12(4y2y)=12(2y)=12y=2×21y=4.\Rightarrow \Big(\dfrac{6}{x} + \dfrac{4}{y}\Big) - \Big(\dfrac{6}{x} + \dfrac{2}{y}\Big) = 0 - \dfrac{1}{2} \\[1em] \Rightarrow \Big(\dfrac{6}{x} + \dfrac{4}{y} - \dfrac{6}{x} - \dfrac{2}{y}\Big) = -\dfrac{1}{2} \\[1em] \Rightarrow \Big(\dfrac{4}{y} - \dfrac{2}{y}\Big) = -\dfrac{1}{2} \\[1em] \Rightarrow \Big(\dfrac{2}{y}\Big) = -\dfrac{1}{2} \\[1em] \Rightarrow y = \dfrac{2 \times 2}{-1} \\[1em] \Rightarrow y = -4.

Substituting value of y in equation (1),

2x+23(4)=162x16=162x=16+162x=262x=13x=2×3x=6.\Rightarrow \dfrac{2}{x} + \dfrac{2}{3(-4)} = \dfrac{1}{6} \\[1em] \Rightarrow \dfrac{2}{x} - \dfrac{1}{6} = \dfrac{1}{6} \\[1em] \Rightarrow \dfrac{2}{x} = \dfrac{1}{6} + \dfrac{1}{6} \\[1em] \Rightarrow \dfrac{2}{x} = \dfrac{2}{6} \\[1em] \Rightarrow \dfrac{2}{x} = \dfrac{1}{3} \\[1em] \Rightarrow x = 2 \times 3 \\[1em] \Rightarrow x = 6.

Hence, x = 6, y = -4.

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