2421.sagews

P, T, v, R, a, b = var('P T v R a b')

eq1 = P==(R*T/(v-b))-(a/v^2)

eq2 = 0==-((R*T)/(v-b)^2)+2*a/v^3

eq3 = 0==((2*R*T)/(v-b)^3)-6*a/(v^4)

solve([eq1,eq2,eq3],P,T,v)

[[P == r2, T == 0, v == b], [P == 1/27*a/b^2, T == 8/27*a/(R*b), v == 3*b]]