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Mathematics

Solve the following systems of simultaneous linear equations by the elimination method

3x+4y=7\dfrac{3}{x} + 4y = 7

5x+6y=13\dfrac{5}{x} + 6y = 13

Linear Equations

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Answer

Given,

3x+4y=7\dfrac{3}{x} + 4y = 7 …….(i)

5x+6y=13\dfrac{5}{x} + 6y = 13 …….(ii)

Multiplying eq. (i) by 3 and eq. (ii) by 2 we get,

9x+12y=21\dfrac{9}{x} + 12y = 21 ……(iii)

10x+12y=26\dfrac{10}{x} + 12y = 26 …….(iv)

Subtracting eq. (iii) from (iv) we get,

10x9x+12y12y=26211x=5x=15.\Rightarrow \dfrac{10}{x} - \dfrac{9}{x} + 12y - 12y = 26 - 21 \\[1em] \Rightarrow \dfrac{1}{x} = 5 \\[1em] \Rightarrow x = \dfrac{1}{5}.

Substituting value of x in eq. (i) we get,

3x+4y=7315+4y=715+4y=74y=8y=2.\Rightarrow \dfrac{3}{x} + 4y = 7 \\[1em] \Rightarrow \dfrac{3}{\dfrac{1}{5}} + 4y = 7 \\[1em] \Rightarrow 15 + 4y = 7 \\[1em] \Rightarrow 4y = -8 \\[1em] \Rightarrow y = -2.

Hence, x = 15\dfrac{1}{5} and y = -2.

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