Proportion in harmonic progression

If $a$ , $b$ , $c$ are in harmonic progression, show that $a : (a - b) = (a + c) : (a - c)$ .

~4 minProof · checked by AIHarmonic progressionProportion

H. S. Hall & S. R. Knight, Higher Algebra (1891) · Ch. VI. Harmonical Progression, Examples VI.a, No. 6

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