Solve each of the following systems of equations by using the method of cross multiplication:

We have,

…(i)


…(ii)


Let 1/(x + y) = p and 1/(x - y) = q. Now,


From equation (i), 5p – 2q + 1 = 0 …(iii)


From equation (ii), 15p + 7q – 10 = 0 …(iv)


From equation (iii), we get a1 = 5, b1 = - 2 and c1 = 1


And from equation (iv), we get a2 = 15, b2 = 7 and c2 = - 10


Using cross multiplication,







and


and


p = 1/5 and q = 1


and [ p = 1/(x + y) and q = 1/(x - y)]


To solve these, we need to take reciprocal of these equations. By taking reciprocal, we get


x + y = 5 and x – y = 1


Rearranging them again,


x + y – 5 = 0 …(v)


x – y – 1 = 0 …(vi)


From equation (v), we get a1 = 1, b1 = 1 and c1 = - 5


And from equation (vi), we get a2 = 1, b2 = - 1 and c2 = - 1


Using cross multiplication,







and


and


x = 3 and y = 2


Thus, x = 3, y = 2


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