actually im a beginner in music, but not that beginner, I know some chord and music theory, but I got doubt when I was playing keyboard, how to play the bass? is the bass in the left hand? and is the chord on right hand? if the chord: D7 Dm C D7 Dm C G/B I know all these chord, but I want to know exactly to play that. If I want to play a music, Am I have to browse the staff or the chord. I really need help.
Yes the bass is generally played with the left hand on the keyboard, when played with 2 hands. I think your question is very general because these rules can always be broken, i.e,. the chords can be played in the right hand and the melody played with the left, but allow me to clarify something.
The bass isn't necessesarily dependent on the hand you play it on but more that it is supporting the harmonic structure of the music. In most music, the bass is the root of the chord (the "C" in C maj, the "A" in A min, etc...) but you can add variation and complexity by having the bass do inversions of the chord by playing the 3rd, 5th, or 7th. This adds different texture and tension to music.
When trying to figure out if a note should be played with your right or left hand on a 88 key piano, the general rule of thumb is that, notes below middle C should be played with your left hand, and notes above middle C with your right. There are of course exceptions to this in certain passages but this should help get you started initially.
If all you're given is chords, then you don't really have enough information to go on to answer that question. It's up to you to pick the chord inversions/voicings and decide how high or low to play them, and so on.
One simple way to play that Dm, for example, might be to play D4-F4-A5 in the right hand and D3 in the left hand. The C would be C4-E4-G4 plus C3; etc. This is very basic but generally gives the right kind of sound. If you have access to the melody notes you could change the inversions to match them accordingly, or you could play only the melody in the right hand and use chords in the left.
I should also note that slash chords, like the G/B you mention, do give a little more information — namely, that the bass note is typically the one that comes after the slash (B in this case).