大概意思是这样Plot[4 (a b t2 - t1 t2 (r + t2)) (b^2 t2 + a^2 (-r + t2) +
a r (r + t2) - b r (r + t2) - 6 t1 t2 (r + t2) +
a b (r + 4 t2)), {r, 0, 1}], {a, 0, 1}, {b, 0, 1}, {t1, 0, 1}, {t2, 0, 1},
{a^2 (r - t2) + b^2 (r - t2) + 8 t1 t2 (r + t2) -2 a b (r + 3 t2) < 0}]