- #1
priceofcarrot
- 32
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Hi, so this isn't a question, it's just an example that they've given, but I don't understand the explanation given.
You have :
y = x^2 - 4
x = y^2 - 4
y^2 = x + 4
y = ± sqrt(x+4)
I don't get why there is a ± symbol there. My book says that it's necessary because there are two values for y that will satisfy the equation, and that if x = 0, y could be +2 or -2.
I understand that y could = +2, because sqrt 4 = +2, but I don't see how it could equal -2.
How would I know that I should include the ± symbol in front of the sqrt(x+4)? Thanks