Solve a + b = 90 for b

The ratio pv to nrt is plotted against pressure for ch4 at 0°c and 200°c. why does the curve for 0°c drop below the horizontal line for an ideal gas whereas the curve for 200°c does not?

Which expression gives you the distance between the points (5,1)and(9,-6)

Solve each equation using the quadratic formula. find the exact solutions. 6n^2 + 4n - 11