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Factor the trinomial.


Select the correct choice below.

(a) x^2-x-20=?

(b) The polynomial is prime.

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1 Answer

Because a quadratic trinomial can have two solutions, x1 and x2, it can ve factored in the following way

                         x^2 -x -20 = (x -x1)(x-x2)   (when the first coefficient in the trinomial is equal 1)

 x1 and x2 are factors of -20 such that x1 +x2 = -(-1) =1. It is easy to see that  x1 = 5, x2 = -4.

                 Thus, we have    x^2 - x - 20 = (x-5)(x+4)