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# What two numbers add to give − 9 −9 and multiply to give 18 18 ?

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What two numbers add to give − 9 −9 and multiply to give 18 18 ? \\What two numbers add to give − 9 −9 and multiply to give 18 18 ?
Mar 16, 2023

#1
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hello

To find two numbers that add to give -9 and multiply to give 18, we can use algebraic equations.

Let's call the two numbers we're looking for "x" and "y". Then we can write:

x + y = -9 (equation 1)
xy = 18 (equation 2)

We can solve equation 1 for one of the variables. For example, we can solve for "x" by subtracting "y" from both sides:

x = -9 - y

We can then substitute this expression for "x" into equation 2, giving:

(-9 - y)y = 18

Expanding the left-hand side and rearranging, we get:                         Nexus Iceland App

y^2 + 9y - 18 = 0

This is a quadratic equation that we can solve using the quadratic formula:

y = (-9 ± sqrt(9^2 - 4(1)(-18))) / (2(1))

Simplifying:

y = (-9 ± 15) / 2

So we have two possible values for "y":

y = -12 or y = 3/2

If y = -12, then we can use equation 1 to find x:

x + (-12) = -9
x = 3

So one possible pair of numbers that add to give -9 and multiply to give 18 is 3 and -12.

If y = 3/2, then we can use equation 1 to find x:

x + (3/2) = -9
x = -21/2

So another possible pair of numbers that add to give -9 and multiply to give 18 is -21/2 and 3/2.

Therefore, there are two possible pairs of numbers that add to give -9 and multiply to give 18: {3, -12} and {-21/2, 3/2}.

Mar 16, 2023
#2
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@wisdom321:  Note that your equation, y^2 + 9y - 18 = 0, shoud be y^2 + 9y + 18 = 0

Alan  Mar 16, 2023