What two numbers multiply to -640 and add up to 639?

Here we answer the question: "What two numbers multiply to -640 and add up to 639?"

The answer to your question is:

-1 and 640

Below we illustrate and prove that -1 and 640 multiply to -640 and add up to 639:

-1 × 640 = -640
-1 + 640 = 639

Are you asking because you are trying to figure out how to factor the following quadratic equation?

x² + 639x - 640 = 0

If so, the solution to factor the quadratic equation above is:

(x - 1 ) (x + 640)

To summarize, since -1 and 640 multiply to -640 and add up 639, you know that the following is true:

x² + 639x - 640 = (x - 1 ) (x + 640)

Multiply To One Number and Add Up To Another
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