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Trebla

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This isn't a "shorter way" per se, but is an alternative if you're really that lazy to expand...

Let . Since is a root of the polynomial then





Since we get same result regardless of whether we define y in terms of then this new equation has the roots .

Hence is just the product of the roots of that new equation.

By inspection of the expansion we can see that the constant term is -1- 4-16+56, or equivalently 35. The product of the roots is therefore -35.
 

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