To find the answer to "What two numbers have a product of 15 and a sum of -10?" we first state what we know. We are looking for x and y and we know that x • y = 15 and x + y = -10.
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 = -10 and solve it for y to get y = -10 - x. Then, we replace y in x • y = 15 with -10 - x to get this:
x • (-10 - x) = 15
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 15 and a sum of -10. The numbers are:
-8.16228
-1.83772
That's it! The two numbers that have a product of 15 and a sum of -10 are -8.16228 and -1.83772 as proven below:
-8.16228 • -1.83772 ≈ 15
-8.16228 + -1.83772 = -10
Note: Answers are rounded up to the nearest five decimals if necessary so the answers may not be exact.
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