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smc

counting and probability senior

Problem

We define a lattice point as a point whose coordinates are integers, zero admitted. Then the number of lattice points on the boundary and inside the region bounded by the -axis, the line , and the parabola is:
(A)
(B)
(C)
(D)
Solution
We want to find the number of lattice points in and on the boundary of the shaded region in the diagram. To do this, we will look at the integer values of from to . At a given value of , the amount of lattice points in the region is , because all of the integers from up to and including are in the region. Thus, evaluating this expression at at and and adding the results together, we see that the number of lattice points is , so our answer is .
Final answer
B