Question

5/x+y - 2/x-y = -1 ; 15/x+y - 7/x-y =10 then x-y = ?​

Answer 1

→Answer :

The given equations are 5/ x+y - 2/ x-y = -1 ……(i) 15/ x+y - 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 (∵ 1/ x-y = ) …..(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.

Answer 2

Multiple with 3 of 1st equation and then solve both equations. x-y = -1/3