Question

How do you subtract `\frac { 4} { 2r ^ { 4} s ^ { 5} } - \frac { 5} { 9r ^ { 3} s ^ { 7} }`?

Answer 1

`color(purple)(=>(18s^2 - 5r) / (9r^4s^7)`

Explanation:

First let's find the L C M or L C D of `2r^4s^5 , 9 r^3 s^7`

`L C M = 2 * 9 * r^4 * s ^ 7`

`4 / (2r^4s^5) - 5 / (9 r^3 s^7) = (4 * 9 * s^2 - 5 * 2 * r)/ (18 r^4s^7)`

`=> (36s^2 - 10r) / (18r^4s^7)`

`=> (cancel2 * (18s^2 - 5r)) / (cancel2 * 9 r^4s^7`

`color(purple)(=>(18s^2 - 5r) / (9r^4s^7)`