difference between formulas ?

there is a formula for calculating cost of equity and it goes Ke=(d0(1+g)/p0)+g

and there is a formula that you can find on the formula table given at the exam and it goes

P0=d0(1+g)/ri-g There was a question in December 2010 no.4 where they used this formula to calculate the value of the equity ,I was tricked and I was trying to solve the question by the formula first above . Can u help me better understand the difference between two formulas?