Help I’d help a lot thank u very much

The two terms must have a subtraction sign between them, hence the "difference" in "difference of squares". Also, the two terms must be perfect squares. In the case of choice D we have

100x^2 = (10x)^2

49y^2 = (7y)^2

So 100x^2 - 49y^2 = (10x)^2 - (7y)^2. It is now in the form a^2-b^2 and we'll use the difference of squares factoring rule

a^2 - b^2 = (a-b)(a+b)

Something like 55 is not a perfect square since sqrt(55) = 7.416 approximately is not a whole number.

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step-by-step explanation: