Question

4/x +5/y=7;3/x+4/y=5

Answer 1

solution:

4/x+5/y=7 | 3/x+4/y=5
5x+4y=7...1steq. | 4x+3y=5...2nd eq.

by elimination method

5x+4y=7
4x+3y=5

multiplying 1st by 4 and 2nd by 5
20x+16y=28
20x+15y=25
subtracting the eq. we get,
y=3
now substituting the value of y in 1st
we get,
x=-1

Answer 2

4/x+5/y=7----(eqn 10)

3/x+4/y=5----(eqn 2)

Now,put 1/x=m and 1/y=n

   from eqn 1

4m+5n=7-----eqn 3

   from eqn 2

3m+4n=5-----(eqn 4)

multiply eqn 3 by 3

12m+15n=21---(eqn 5)

multiply eqn 4 by 4

12m+16n=20---(eqn 6)

substract eqn 6 from eqn 5

   12m+15n=21

-   12m+16n=20

-------------------------------

          -1n=1

        n=   -1

now,put value of n= -6 in (eqn 3)

    4m+5(-1)=7

    4m+(-5)=7

    4m=7+5

    4m=12

   m=3