Answer:
LCM of 6 and 15 by Listing Multiples
Step 2: The common multiples from the multiples of 6 and 15 are 30, 60, . . . Step 3: The smallest common multiple of 6 and 15 is 30.
Answer:
rate of exchange is -2/-2
When taking square roots, you can't take square roots of negative roots of negative numbers. So, what will work for the domain of u(x) is what makes u(x) zero or more. We can make an inequality for that.
u(x) ≥ 0.

9x + 27 ≥ 0 by squaring both sides
9x ≥ -27
x ≥ -3
So the domain of the function is when x ≥ -3 is true.
First, note that

is always positive (except for x=0), so

must be always negative.
Thus, the only plausible graphs are 1 and 3 since they are below the x-axis.
Now,

and

are only defined for x≥0, because only for these x'es we can take the square root.
Note that the third graph has domain (-infinity, 0], so it is not the right one, while 1 is ok.
Answer: first graph
Do you have a calculator to plug it into? What are you learning