1.

Solve for x and y:\(\frac{10}{x+y}+\frac{2}{x-y}=4\),\(\frac{15}{x+y}-\frac{9}{x-y}=-2\),where x ≠ y, x ≠ -y.

Answer»

The given equations are

 \(\frac{10}{x+y}+\frac{2}{x-y}=4\).............(i)

\(\frac{15}{x+y}-\frac{9}{x-y}=-2\).......(ii)

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

10u + 2v = 4 ……..(iii) 

15u - 9v = -2 …….(iv) 

Multiplying (iii) by 9 and (iv) by 2 and adding, we get: 

90u + 30u = 36 – 4

⇒120u = 32 

⇒u = 32/120 = 4/15 

⇒x + y = 15/4 \((∵\frac{1}{x+y}=u)\).........(v)

On substituting u = 4/15 in (iii), we get: 

10 × 4/15 + 2v = 4 

8/3 + 2v = 4 

⇒2v = 4 - 8/3 = 4/3 

⇒v = 2/3 

⇒ x – y = 3/2 \((∵\frac{1}{x-y}=v)\)........(vi)

Adding (v) and (vi), we get 

2x = 15/4 + 3/2 ⇒2x = 21/4 ⇒x = 21/8 

Substituting x = 21/8 in (v), we have 

21/8 + y = 15/4 ⇒y = 15/4 - 21/8 = 9/8 

Hence, x = 21/8 and y = 9/8



Discussion

No Comment Found