Question

Factor x2 – 2x – 80.

A. (x – 3)(x + 10)
B. (x + 6)(x - 1)
C. (X + 8)(x - 10)
D. (+3)(x+6)

Answer 1

Answer: C. (x+8)(x-10)

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Step-by-step 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.

Answer 2

(x-10) (x+8)

Step-by-step explanation:

x^2 – 2x – 80.

What two numbers multiply to -80 and add to -2

-10*8 = -80

-10+8 = -2

(x-10) (x+8)