I have two questions, trying to learn to do DE's using substitution....my problems ussally come out looking like horrbile bog monsters of intergation (like a parts of x^9 (e^x)) i could intergrate it but id like to keep my work to under 3 pages .....anyway:

i have a (dy/dx) = cos (x+y)

and

dy/dx - y/x = y^3

also i have one wth the dentotation "any appropriate method" and i trie excat and came out with the above explained bog monster....

it starts ...(x(dy/dx))-4y=x^6(e^x)

Thanks agian all, any help would be appreciated....