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Mathematics

Solve :

5x+8y=195x + \dfrac{8}{y} = 19

3x4y=73x - \dfrac{4}{y} = 7

Linear Equations

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Answer

Given, equations :

5x+8y=19\Rightarrow 5x + \dfrac{8}{y} = 19 ………(1)

3x4y=7\Rightarrow 3x - \dfrac{4}{y} = 7 ……..(2)

Multiplying equation (2) by 2, we get :

2(3x4y)=2×76x8y=14 ……..(3)\Rightarrow 2\Big(3x - \dfrac{4}{y}\Big) = 2 \times 7 \\[1em] \Rightarrow 6x - \dfrac{8}{y} = 14 \text{ ……..(3)}

Adding equation (1) and (3), we get :

(5x+8y)+(6x8y)=19+145x+6x+8y8y=3311x=33x=3311=3.\Rightarrow \Big(5x + \dfrac{8}{y}\Big) + \Big(6x - \dfrac{8}{y}\Big) = 19 + 14 \\[1em] \Rightarrow 5x + 6x + \dfrac{8}{y} - \dfrac{8}{y} = 33 \\[1em] \Rightarrow 11x = 33 \\[1em] \Rightarrow x = \dfrac{33}{11} = 3.

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

5×3+8y=1915+8y=198y=19158y=4y=84=2.\Rightarrow 5 \times 3 + \dfrac{8}{y} = 19 \\[1em] \Rightarrow 15 + \dfrac{8}{y} = 19 \\[1em] \Rightarrow \dfrac{8}{y} = 19 - 15 \\[1em] \Rightarrow \dfrac{8}{y} = 4 \\[1em] \Rightarrow y = \dfrac{8}{4} = 2.

Hence, x = 3 and y = 2.

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