Answer:
(a) (a² +3a -1)(a² -3a -1)
Step-by-step explanation:
The constant term of the product of the factors will be equal to the product of their constants. Since you want that product to be +1, the signs of the factor constants must be the same. That eliminates choices (c) and (d).
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To tell which of choices (a) and (b) is correct, we can compute the squared term in their product. Let's do it in a generic way, with the constant (±1) being represented by "c".
We want the a² term in the product ...
(a² +3a +c)(a² -3a +c)
That term will be the result of multiplying both sets of first and last terms, and adding the product of the middle terms:
(a²·c) +(a²·c) -9a² = a²(2c-9)
So, we want the factor (2c-9) to be -11, which means c=-1, not +1.
The correct factorization of the given expression is ...
(a² +3a -1)(a² -3a -1) . . . . matches choice A
