Answer: C. (x+8)(x-10)
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Explanation:
The last term is -80 and the middle coefficient is -2
Find two numbers that
- Multiply to -80, and,
- add to -2
Those two numbers are 8 and -10
- 8 times -10 = -80
- 8 plus -10 = -2
which is why the original expression factors to (x+8)(x-10)
We can use the FOIL rule to expand out (x+8)(x-10) to end up with x^2-10x+8x-80 = x^2-2x-80, which confirms we have the correct factorization. You can use the box method as an alternative.
