how to calcuate 2way stakes with bias

[coletek]

I know how to calculate 2way stakes via:

ur1 = 100 / odds_1
ur2 = 100/ odds_2
stake_1 = ur1 / (ur1 + ur2)
stake_2 = ur2 / (ur1 + ur2)

But how do I calculate stake_1 and stake_2, for a bias on odds_1, or bias on odds_2 ?