Let a be a moving point on the ellipse x ^ 2 / A ^ 2 + y ^ 2 / b ^ 2 = 1, and the chords AB and AC pass through the focus F1 and F2 respectively. When AC is perpendicular to the X axis, there is exactly | AF1 |: | af2 | = 3:1, (1) find the eccentricity of the ellipse (2) Let AF1 = mf1b, af2 = nf2c, and prove that M + n is the fixed value 6 (all letters are vectors)

Let a be a moving point on the ellipse x ^ 2 / A ^ 2 + y ^ 2 / b ^ 2 = 1, and the chords AB and AC pass through the focus F1 and F2 respectively. When AC is perpendicular to the X axis, there is exactly | AF1 |: | af2 | = 3:1, (1) find the eccentricity of the ellipse (2) Let AF1 = mf1b, af2 = nf2c, and prove that M + n is the fixed value 6 (all letters are vectors)

1. Let AF1 = 3T, then af2 = t, F1F2 = 2C = 2 √ 2T, that is, C = √ 2T. ① n = 1, this is simple; ② it is proved that M = 5: with the above