To factor the polynomial \( 16x^8 - 49x^2 \), we can recognize that it resembles the form of a difference of squares. The difference of squares pattern is expressed as:
\[ a^2 - b^2 = (a - b)(a + b) \]
In this case, we can rewrite \( 16x^8 - 49x^2 \) as follows:
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Identify \( a \) and \( b \):
- \( a^2 = 16x^8 \) → \( a = 4x^4 \)
- \( b^2 = 49x^2 \) → \( b = 7x \)
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Now we apply the difference of squares formula:
\[ 16x^8 - 49x^2 = (4x^4)^2 - (7x)^2 = (4x^4 - 7x)(4x^4 + 7x) \]
Thus, the original expression can be factored into:
\[ (4x^4 - 7x)(4x^4 + 7x) \]
Therefore, the correct response indicating the pattern used to factor \( 16x^8 - 49x^2 \) is:
\[ (a - b)(a + b) = a^2 - b^2 \]
So, the correct answer would be:
\[ (a-b)(a+b)=a^2-b^2 \quad \text{(the difference of squares)} \]