Is (3y+13) a factor constant or coefficient

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?

Use set buikder notation to represent the following set: {, -2, -1, 0}

Which graph corresponds to the function f(x) = x2 + 4x – 1?