Math Question

[geoschmo]

Originally posted by Cipher7071:

quote:

---

But isn't there always a positive AND negative number for any square root? If x is 0 for example you get f(0)=sqrt(4) Isn't that 2 or -2? Can someone explain why you don't count the -2?

Geo, this is probably because you are working with functions. A function may only have one value in the range for each value in the domain.
So, in this case, the function sqrt() is defined to be positve .

---

Ok, but isn't that circular logic? To me it sounds like you are saying that the square root of a number is always positive, because if it's negative then it's not a function. But the square root being positive is what makes it a function. How do you know it's a function, other then the fact that I typed it in function notation? Because there are times they will give you a problem in function notation and ask you if it is indeed a function.