Which of the following shows that polynomials are closed under addition when two polynomials 4x2 − 8x − 7 and −5x + 16 are added?
4x2 − 13x + 9 may or may not be a polynomial.
4x2 + 13x − 23 may or may not be a polynomial.
4x2 − 13x + 9 will be a polynomial.
4x2 + 13x − 23 will be a polynomial.

Period is the time it takes for one “cycle” to complete. in the parent sine function, period is 2*pi since sin(0) = 0, sin(pi/2) = 1, sin(pi) = 0, sin(3pi/2) = -1, and sin(2pi) = 0. at that point, the sequence repeats itself. i’m not sure if your graph is similar to the sine function since you didn’t provide a picture, but you can find the period by looking at a graph.