If the quadratic function y = f (x) satisfies f (3 + x) = f (3-x), and f (x) = 0 has two real roots X1 and X2, then X1 + x2 = () A. 0b. 3C. 6D. Not sure

If the quadratic function y = f (x) satisfies f (3 + x) = f (3-x), and f (x) = 0 has two real roots X1 and X2, then X1 + x2 = () A. 0b. 3C. 6D. Not sure

∵ quadratic function y = f (x) satisfies that f (3 + x) = f (3-x). The image of the function is symmetric with respect to x = 3, ∵ f (x) = 0 has two real roots X1 and X2, and these two real roots are symmetric with respect to the axis of symmetry, ∵ X1 + x2 = 2 × 3 = 6, so C is selected