What is the curve : y= -2x

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?

If abcde is reflected over the x-axis and then translated 3 units left, what are the new coordinates d?

Find the condition that the zeros of the polynomial f(x) = x^3+3px^2+3px+r may be in a. p.