Here the denominators are quadratics , so we need to factorise them first
1/(x²-5x) +3/(x²+2x-35)
factorising x²-5x ,
here GCF is x, so taking x out we have
x(x-5)
factorising x²+2x-35 using AC method,
we find factors of -35 that add up to give 2
(x-5)(x+7)
Since we have x-5 common in both denominators, so lcd of the rational expression will be product of x(x-5)(x+7)
lcd is x(x-5)(x+7)