Hello, c_323_h!

If you're doing these "by parts", there isn't any choice.

. . So what the problem?

Let:

Then:

And we have: .

. . .

Can you finish it now?

Let:

Then:

And we have: .

Let:

Then:

And we have: .

. . .

. . . . . . . . . . . . . and this can be done by parts