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If 10/x + y + 2/x - y = 4 and 15/x + y - 5/x - y = -2 thenA) x = 3, y = 2 B) x = 3, y = -2 C) x = -3, y = 2 D) x = -3, y = -2 |
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Answer» Correct option is (A) x = 3, y = 2 \(\frac{10}{x+y}+\frac{2}{x-y}= 4\) ________(1) and \(\frac{15}{x+y}-\frac{5}{x-y}=-2\) ________(2) Put \(\frac1{x+y}=X\;\&\;\frac{1}{x-y}=Y\) Then equations (1) & (2) converts to 10X + 2Y = 4 ________(3) and 15X - 5Y = -2 ________(4) Multiply equation (3) by \(\frac52,\) we get 25X + 5Y = 10 ________(5) By adding equation (4) & (5), we get (25X + 5Y) + (15X - 5Y) = 10 - 2 \(\Rightarrow\) 40X = 8 \(\Rightarrow\) X \(=\frac8{40}=\frac15\) Then from (3), we get \(10\times\frac15+2Y=4\) \(\Rightarrow\) 2 + 2Y = 4 \(\Rightarrow\) 2Y = 4 - 2 = 2 \(\Rightarrow\) Y = \(\frac22\) = 1 \(\because\) \(X=\frac15\) \(\Rightarrow\) \(\frac1{x+y}=\frac{1}5\) \(\Rightarrow\) x+y = 5 ________(6) and Y = 1 \(\Rightarrow\) \(\frac1{x-y}=1\) \(\Rightarrow\) x - y = 1 ________(7) By adding equations (6) & (7), we get 2x = 5+1 = 6 \(\Rightarrow\) x = \(\frac62\) = 3 \(\therefore\) y = 5 - x = 5 - 3 = 2 Correct option is A) x = 3, y = 2 |
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