How do you find the y-intercept on a graph?

The table below shows the height of a ball  x  seconds after being kicked.  what values, rounded to the nearest whole number, complete the quadratic regression equation that models the data? f(x)  =  x2  +  x  +  0based on the regression equation and rounded to the nearest whole number, what is the estimated height after 0.25 seconds?   feet

Can someone me and do the problem plz so i can understand it more better

The number of fish in a lake can be modeled by the exponential regression equation y=14.08 x 2.08^x where x represents the year