What two numbers multiply to 80 and add up to 21?

Here we answer the question: "What two numbers multiply to 80 and add up to 21?"

The answer to your question is:

5 and 16

Below we illustrate and prove that 5 and 16 multiply to 80 and add up to 21:

5 × 16 = 80
5 + 16 = 21

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

x² + 21x + 80 = 0

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

(x + 5 ) (x + 16)

To summarize, since 5 and 16 multiply to 80 and add up 21, you know that the following is true:

x² + 21x + 80 = (x + 5 ) (x + 16)

Multiply To One Number and Add Up To Another
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