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Functions

by rahul.s » Mon Jan 11, 2010 10:18 pm
The function f is defined by f(x) = sqrt(x - 10) for all positive numbers x. If u = f(t) for some positive numbers t and u. What is t in terms of u?

A) sqrt(u + 10)
B) sqrt[(u + 10)^2]
C) sqrt(u^2 + 10)
D) (u + 10)^2
E) (u^2 + 10)^2

OA: D

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by sanju09 » Tue Jan 12, 2010 12:30 am
First thing first, the statement "f(x) = sqrt(x - 10) for all positive numbers x." is not an ideal GMAT statement; as this would include certain imaginary values for f (x), which GMAT never does. A rectified statement could read "f(x) = sqrt(x - 10) for all positive numbers x ≥ 10."

If f (x) = √(x - 10) then f (t) = √(t - 10)

or u = √(t - 10)

or u^2 = (t - 10)

or t = u^2 + 10.


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by rahul.s » Tue Jan 12, 2010 2:27 am
I guess there's a problem with this question.
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