The number of prisoners held in federal and state prisons, measured in thousands, can be described by the polynomial -2.06x^2 + 77.82x + 743. the variable x represents the number of years since 1990.

a) estimate the number of prisoners in 1990.

b) according to the polynomial, by how much did the prison population increase from 2002 to 2007?

i tried putting 1990 in brackets where the x is for part a, but i got a negative number because of the -2.06 and it's not the right answer. can someone walk me through the steps?