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Algebra Difficulty 4.6 AIME Find the answer

Find all integer solutions to: a+b+c=24,a2+b2+c2=210,abc=440a+b+c=24, a^{2}+b^{2}+c^{2}=210, a b c=440.

A number or a short expression. Spacing and $ signs are ignored.

Solution

ab+bc+ca=((a+b+c)2(a2+b2+c2))/2=183\mathrm{ab}+\mathrm{bc}+\mathrm{ca}=\left((\mathrm{a}+\mathrm{b}+\mathrm{c})^{2}-\left(\mathrm{a}^{2}+\mathrm{b}^{2}+\mathrm{c}^{2}\right)\right) / 2=183, so a,b,c\mathrm{a}, \mathrm{b}, \mathrm{c} are roots of the cubic x324x2+183x440=0\mathrm{x}^{3}-24 \mathrm{x}^{2} +183 x-440=0. But it easily factorises as (x5)(x8)(x11)=0(x-5)(x-8)(x-11)=0, so the only solutions are permutations of (5,8,11)(5,8,11).

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Source: NuminaMath-1.5, licensed Apache-2.0. Statement and solution reproduced as published; topic and difficulty added by this site.