-57
We can collect terms to simplify the arithmetic.
... = a^3(6 +4 -8) +a^10(-1 +1) +a
... = 2a^3 +a
... = a(2a^2 +1)
For a = -3, this is
... -3(2(-3)² +1) = -3(2·9 +1)
... = -3·19 = -57
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