# Find Value(s) of x

Discussion in 'Other Pre-University Math' started by nycmathguy, Nov 14, 2021.

1. ### nycmathguy

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David Cohen

Let me see if I can at least get started.

y = sqrt{f(x)}

y = sqrt{(x - 1)^2 - 4}

To find the domain, I must set (x - 1)^2 - 4 to be => 0.

Yes?

I found the domain to be
(-infinity, -1] U [3, infinity).

If the domain is correct, what is the next step?

nycmathguy, Nov 14, 2021
2. ### MathLover1

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the domain is correct
To minimize something, we have to take its derivative, set it to 0 and solve for x

Last edited: Nov 14, 2021
MathLover1, Nov 14, 2021
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3. ### nycmathguy

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Do I take the derivative of f(x) or sqrt{f(x)}?

nycmathguy, Nov 14, 2021
4. ### MathLover1

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sqrt{f(x)}

MathLover1, Nov 14, 2021
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5. ### nycmathguy

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d/dx [(x - 1) - 4] = 2(x - 1).

2 (x - 1) = 0

2x - 2 = 0

2x = 2

x = 2/2

x = 1

Yes?

nycmathguy, Nov 14, 2021
6. ### MathLover1

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x = 1

Yes

MathLover1, Nov 14, 2021
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7. ### nycmathguy

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Very cool. A little calculus there.

nycmathguy, Nov 14, 2021
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