Answer is option D.
Explanation:
The best way to know which graph represents the equation mentioned, you can put some values of x in the equation and evaluate the value of y(or f(x));
In the given example, if we plug 2 in the place of x, f(x) will be 2. The point on the graph should be (2,2) which is present in graph 4. If we plug 4 into the equation, f(x) will be 8. The point on the graph should be (4,8) which is present in graph D only.
The calculation is pretty straight forward in this but do some more calculations like above if there is a need.
The probable question can be: Which graph represents f(x)=1/2x2 ?