Question

Which value of x is in the domain of f(x)=√x - 15?

O A. x= -15
O B. x= 1
O'C. x = 0
O D. x = 16

Answer 1

Answer: Choice D) x = 16

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Step-by-step explanation:

I'm assuming you meant to say
`f(x) = √(x-15)` where the square root is over all of x-15, and not just x.

If so, then we set the x-15 greater than or equal to zero

`x-15 \ge 0\\\\x \ge 15`

Add 15 to both sides to isolate x. This is done to ensure the x-15 is 0 or larger. The domain is the set of x values such that x = 15 or x > 15

The values -15, 1 and 0 won't work. But x = 16 does work which is why choice D is the answer

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Put another way: Choices A through C make the x-15 to be negative; but we cannot have a negative number under the square root (if we want f(x) to be a real number). So we eliminate choices A through C.

Choice D has x-15 be some nonnegative result, which is why it's in the domain.