How do you find the diameter of a quarter circle?

The graph of f(x), shown below, resembles the graph of g(x) = x2, but it has been changed somewhat. which of the following could be the equation of f(x)?

Which of the following is correct interpretation of the expression -4+13

Acertain volume of water contains 100000 hydrogen atoms and 50,000 oxygen atoms how many hydrogen atoms are in a volume of water containing 4 million oxygen atoms