Solve for x and y:
We have
and
Lets simplify these equations. Assuming p = 1/(x + y) and q = 1/(x – y),
10p + 2q = 4 …(i)
Also,
⇒ 15p – 9q = - 2 …(ii)
To solve these equations, we need to make one of the variables (in both the equations) have same coefficient.
Lets multiply eq.(i) by 9 and eq.(ii) by 2, so that variable q in both the equations have same coefficient.
Recalling equations (i) & (ii),
10p + 2q = 4 [×9]
15p – 9q = - 2 [×2]
⇒ 120p = 32
⇒ p = 4/15
Substitute p = 4/15 in eq.(i)/eq.(ii), as per convenience of solving.
Thus, substituting in eq.(ii), we get
15(4/15) – 9q = - 2
⇒ 4 – 9q = - 2
⇒ 9q = 4 + 2 = 6
⇒ q = 2/3
Thus, p = 4/15 and q = 2/3
As p = 1/(x + y),
⇒
⇒ 4x + 4y = 15 …(iii)
And q = 1/(x – y)
⇒
⇒ 2x – 2y = 3 …(iv)
Multiplying eq.(iv) by 2, we get
4x – 4y = 6 …(v)
and then adding equations (iii) and (v) to obtain x and y,
(4x + 4y) + (4x – 4y) = 6 + 15
⇒ 8x = 21
⇒ x = 21/8
Putting the value of x in equation (iv), we get
2(21/8) – 2y = 3
⇒ 21/4 – 2y = 3
⇒ 2y = 21/4 – 3 = 9/4
⇒ y = 9/8
Hence, we have x = 21/8 and y = 9/8