Question

add and simplify
4d 9d
------- + -------
5d -10 10d -20

Answer 1

need a common denominator
5d - 10 factors into 5(d - 2)

10d - 20 factors into 10(d - 2)
10(d - 2) can be written as 2 * 5 * (d - 2)

So... common denominator is 2 * 5 * (d - 2) or 10(d - 2) = 10d - 20

So to make 5d - 10 into 10d - 20, you would multiply by 2 so take the top and bottom times 2 on the first fraction.

8d 9d
-------- + --------
10d - 20 10d - 20

17d
-------
10d - 20

Answer 2

Thanks