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# Square Root watch

1. Okay, if you have , does that imply a +- of the root itself, or just the positive root? I ask this because I've been asked to sketch such graph and the solution only includes the sketch above the x-axis. The question did not restrict the range or anything.
2. (Original post by ViralRiver)
Okay, if you have , does that imply a +- of the root itself, or just the positive root? I ask this because I've been asked to sketch such graph and the solution only includes the sketch above the x-axis. The question did not restrict the range or anything.
That's just an expression? Did you mean to say "sketch ? If so, you only sketch the positive part because the RHS is clearly just positive.

The confusion you're having is that if you're just given something as a surd, it is always positive. Whereas, if you had and then took the square root of both sides, you would have and would thus have to sketch both the positive and negative parts of the graph.
3. (Original post by ViralRiver)
Okay, if you have , does that imply a +- of the root itself, or just the positive root? I ask this because I've been asked to sketch such graph and the solution only includes the sketch above the x-axis. The question did not restrict the range or anything.

http://www.wolframalpha.com/input/?i=%28x^2%2B16%29^-5

You will find the graph there as well.
4. Okay, so if you had and you rewrote it as , then clearly you're ignoring one of the roots. Is there anyway to get round that with indices, and avoiding the square root symbol?
5. (Original post by ViralRiver)
Okay, so if you had and you rewrote it as , then clearly you're ignoring one of the roots. Is there anyway to get round that with indices, and avoiding the square root symbol?
If you're solving that top equation for y in terms of x, then yes you are ignoring the negative root.

It's not a case of getting around it. The only way you can discard it is if you define y>0.

If I'm honest, I'm not sure what your query is. What do you mean by "get around it"?

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