1.

Solve for x and y:\(\frac{5}{x+y}-\frac{2}{x-y}=-1\),\(\frac{15}{x+y}-\frac{7}{x-y}=10\)

Answer»

The given equations are

 \(\frac{5}{x+y}-\frac{2}{x-y}=-1\).......(i)

\(\frac{15}{x+y}-\frac{7}{x-y}=10\)......(ii)

Substituting 1/x+y = u and 1/x−y = v in (i) and (ii), we get 

5u – 2v = -1 ……..(iii) 

15u + 7v = 10 …….(iv) 

Multiplying (iii) by 3 and subtracting it from (iv), we get 

7v + 6v = 10 + 3 

⇒ 13v = 13 

⇒ v = 1

⇒x – y = 1 \((∵\frac{1}{x-y}=v)\)......(v)

Now, substituting v = 1 in (iii), we get 

5u – 2 = -1 

⇒5u = 1 

⇒u = 1/5 

x + y = 5 …….(vi) 

Adding (v) and (vi), we get 

2x = 6 ⇒ x = 3 

Substituting x = 3 in (vi), we have 

3 + y = 5 ⇒ y = 5 – 3 = 2 

Hence, x = 3 and y = 2.



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