What two numbers multiply to -640 and add up to 123?

Here we answer the question: "What two numbers multiply to -640 and add up to 123?"

The answer to your question is:

-5 and 128

Below we illustrate and prove that -5 and 128 multiply to -640 and add up to 123:

-5 × 128 = -640
-5 + 128 = 123

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

x² + 123x - 640 = 0

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

(x - 5 ) (x + 128)

To summarize, since -5 and 128 multiply to -640 and add up 123, you know that the following is true:

x² + 123x - 640 = (x - 5 ) (x + 128)

Multiply To One Number and Add Up To Another
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