What's the domain of y=√7x-4

Question

I've tried many different approaches to this problem but I still can't seem to get it. The answer choices are:

A)x >_ 4

B)x >_ 4/7

C)x <_ 4

D)x <_ 4/7

Answer 1

Do you mean 

 

y = √(7x) - 4

 

or do you mean

 

y = √(7x - 4) ?

 

It makes a big difference!  Use parentheses!  I will assume you really meant

 

y = √(7x - 4)

 

The argument inside the square root must not be negative.  Hence,

 

7x - 4 ≥ 0

7x ≥ 4

x ≥ 4/7

 

That gives you choice (B).