Simplify
Expand the product first. Order of operations puts multiplication before the outer addition:
Combine inside the expansion. , so
Bring in the loose .
Cancel the linear terms. , which removes the linear term completely:
The cancellation is not a coincidence here: the product has middle coefficient , and adding neutralises exactly that.
Check at two values. At : , and . At : , and . As a bonus, is a difference of squares over the reals: .
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