I'm a 21yr old taekwondo athlete. i have to loose 9 pounds in two days. what could be te consecuences of it?

Rapid weight loss: You likely will lose mostly water and then electrolytes. You can become weak and dizzy. Calorie deficit will cause weakness, too.

Likely dehydration: Since it's unlikely that you'll lose 9lbs of body mass and more likely water weight in such a short period of time, you'll likely have symptoms of dehydration like fatigue, headaches, muscle aches or cramps, palpitations, lightheadedness - things of that nature. I would encourage you to consider dropping so much weight so fast. I may greatly diminish your performance.