On a test, a student got 80% of the items correct. If the student got 56 items correct, how many items were on the test?
1 answer:
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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
Thus, the only plausible graphs are 1 and 3 since they are below the x-axis.
Now,
Note that the third graph has domain (-infinity, 0], so it is not the right one, while 1 is ok.
Answer: first graph