What two numbers multiply to -400 and add up to 399?

Here we answer the question: "What two numbers multiply to -400 and add up to 399?"

The answer to your question is:

-1 and 400

Below we illustrate and prove that -1 and 400 multiply to -400 and add up to 399:

-1 × 400 = -400
-1 + 400 = 399

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

x² + 399x - 400 = 0

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

(x - 1 ) (x + 400)

To summarize, since -1 and 400 multiply to -400 and add up 399, you know that the following is true:

x² + 399x - 400 = (x - 1 ) (x + 400)

Multiply To One Number and Add Up To Another
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