If three points a (2,2) B (a, 0) C (0, b) (AB is not equal to 0) are collinear, we prove that 1 / A + 1 / b = 1 / 2

Three points collinear, then
(2-0) / (2-A) = (2-B) / (2-0)
Ab-2b-2a = 0 divided by 2Ab
1/2=1/a+1/b

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