Student: Which of the following is equal to the average (arithmetic mean) of (x+3)^2 and (x-3)^2?\nOptions:\n(A) x^2\n(B) x^2+2\n(C) x^2 +4\n(D) x^2+9\n(E) x^2+4x.
Another student: Let's say, hmmm...

User
Avg = [(x+3)^2 + (x-3)^2] / 2\nExpanding and simplifying, (x^2 + 6x + 9 + x^2 - 6x + 9 ) / 2 = x^2 + 9 Final answer: (D).
Assistant