To find the answer to "What two numbers have a product of -21 and a sum of -64?" we first state what we know. We are looking for x and y and we know that x • y = -21 and x + y = -64.
Before we keep going, it is important to know that x • y is the same as y • x and x + y is the same as y + x. The two variables are interchangeable. Which means that when we create one equation to solve the problem, we will have two answers.
To solve the problem, we take x + y = -64 and solve it for y to get y = -64 - x. Then, we replace y in x • y = -21 with -64 - x to get this:
x • (-64 - x) = -21
Like we said above, the x and y are interchangeable, therefore the x in the equation above could also be y. The bottom line is that when we solved the equation we got two answers which are the two numbers that have a product of -21 and a sum of -64. The numbers are:
-64.32646
0.32646
That's it! The two numbers that have a product of -21 and a sum of -64 are -64.32646 and 0.32646 as proven below:
-64.32646 • 0.32646 ≈ -21
-64.32646 + 0.32646 = -64
Note: Answers are rounded up to the nearest five decimals if necessary so the answers may not be exact.
Product Sum Calculator
Need the answer to a similar problem? Submit another product and sum below to find the two numbers that make your product and sum.