You could find a general equation because you have both points, so it takes less time than checking each of the equations. For this, you have to find the tangent line. A line has an equation in the form of y=m*x+n. In this case, n=0 because one of your points is (0,0), which means that 0=0*m+n. You can then find m by using the second point (1,4). you know that 4=m*1, and the only value of m that checks this is 4, so m=4. Replacing in the original formula you get y=4x, which is the 4th option.