One of the video said that the square root of a number can be negative or positive. But my math teacher said the square root symbol implies only positive numbers. Which would be correct? 

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Well I think your teacher might have meant that only positive numbers have rational square roots so your only squaring positive numbers. But the movie is correct because a negative times a negative equals a positive and a positive times a positive equals a positive. So every positive number has two square roots, a positive one and a negative one.Example:-5*-5=25 5*5=25-7*-7= 497*7=49Hope I helped!

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