Question

If 7x – 15y = 4x + y, find the value of x : y. Hence, use componendo and dividendo to find the values of:

`(9x + 5y)/(9x - 5y)`

Answer 1

7x – 15y = 4x + y

7x – 4x = y + 15y

3x = 16y

`x/y = 16/3`

`=> (9x)/(5y) = 144/15`  ...`("Multiplying both sides by" 9/5)`

`=> (9x + 5y)/(9x - 5y) = (144 + 15)/(144 - 15)`   ...(Applying componendo and dividendo)

`=> (9x + 5y)/(9x - 5y) = (159)/(129) = 53/43`