What is the completely factored form of x squared minus 16 x y plus 64 y squared ?

Recognize the expression as a perfect-square trinomial: x² − 16xy + 64y² = x² − 2(x)(8y) + (8y)². Using a² − 2ab + b² = (a − b)², it factors as (x − 8y)(x − 8y). Choice A gives this completely factored form.

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