已知12已知12已知1212+15 < a+b < 60+3627 < a+b < 9612x2-36 < 2a-b < 60x2-15-12 < 2a-b < 10512/36 < a/b < 60/151/3 < a/b <4
已知1212+15 < a+b < 60+3627 < a+b < 9612x2-36 < 2a-b < 60x2-15-12 < 2a-b < 10512/36 < a/b < 60/151/3 < a/b <4