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Question Number 155356 by qaz last updated on 29/Sep/21
$$\mathrm{Find}\:\mathrm{the}\:\mathrm{coefficient}\:\mathrm{of}\:\mathrm{term}\:``\:\mathrm{a}^{\mathrm{m}} \mathrm{b}^{\mathrm{2m}} \:''\:\mathrm{in}\:\left(\mathrm{1}+\mathrm{a}\right)^{\mathrm{m}} \left(\mathrm{1}+\mathrm{b}\right)^{\mathrm{n}+\mathrm{m}} \left(\mathrm{1}+\mathrm{a}+\mathrm{b}\right)^{\mathrm{m}} . \\ $$