Step-by-step explanation:

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
Answer:
will have a trillionare by that time
Step-by-step explanation:
-2x + 5y = 8
2x + 2y = 6
----------------add
7y = 14
y = 14/7
y = 2
2x + 2y = 6
2x + 2(2) = 6
2x + 4 = 6
2x = 6 - 4
2x = 2
x = 2/2
x = 1
solution is (1,2)