Evaluate
9 - x^2 is greater than or equal to 0.

The question I have about this is that under what conditions is the inequality sign "flipped"? Does it occur here, when you square both sides of the inequality?

Question

Evaluate 
9 - x^2 is greater than or equal to 0.

The question I have about this is that under what conditions is the inequality sign "flipped"? Does it occur here, when you square both sides of the inequality?

anonymous · Answer

the sign is flipped if and only if you multiply the other side by a negative number

anonymous · Answer

Are you sure it doesn't count if you square both sides?

anonymous · Answer

Because the answer I got down for this is [-3,3], but I don't know how the prof. got this.

anonymous · Answer

$$9-x ^{2}\ge0$$
$$-x ^{2}\ge-9$$
$$x ^{2}\le9$$
$$x \le3$$

anonymous · Answer

u understand what i did?

anonymous · Answer

im almost positive thats the answer but i havent looked at this material in a long time

anonymous · Answer

Yes I do understand. Thank you very much.