Expand:
Square the constant first. , so
Pulling the powers of ten out avoids a long multiplication.
Restate as a binomial times a constant.
Only one distribution is left to do.
Distribute, keeping the sign with its term.
Compute the constant term. Use :
Compute the coefficient — it comes out whole.
Because is divisible by , the decimal disappears entirely, so the expansion is with integer coefficients.
Verify at . Original: . Expansion: . The two agree, confirming the result.
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