Factor: 121x^2 - 49y^2.
A(11x-7y)(11x-7y)
B(121x-7y)(x+7y)
C(11x-7y)(11x+7y)
D(11x-49y)(11x+y)
Answer & Solution
Correct answer: C. (11x-7y)(11x+7y)
1. Check that the binomial fits the pattern: 121x squared is (11x) squared, and 49y squared is (7y) squared.
2. Write the product of conjugates using a equals 11x and b equals 7y.
3. Factor to get (11x - 7y)(11x + 7y), and check by multiplying: 121x squared + 77xy - 77xy - 49y squared gives back 121x squared - 49y squared.
_Source: OpenStax Elementary Algebra (CC BY 4.0), Ch 7 "Factoring", section 7.4 Factor Special Products_
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