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SMO 2008 Junior Round 1 Question 23

SMO · SMO 2008 Junior Round 1

Question 23

There are $88$ numbers $a_1,a_2,\ldots,a_{88}$, each equal to either $-3$ or $-1$. Given that $$a_1^2+a_2^2+\cdots+a_{88}^2=280,$$ find $a_1^4+a_2^4+\cdots+a_{88}^4$.