SOLUTION: Hi, I am completely stumped on this question. Please help! What is the number that is 9 less than twice the additive inverse? Thanks!

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Question 523400: Hi,
I am completely stumped on this question. Please help!


What is the number that is 9 less than twice the additive inverse?

Thanks!
Answer by oberobic(2304) About Me  (Show Source):
You can put this solution on YOUR website!
A number plus its additive inverse = 0.
.
What number is 9 less than twice its additive inverse.
.
Define y is the additive inverse of x
so
x + y = 0
so
x = -y
.
The number is 9 less than twice its additive inverse.
x+9 = 2y
.
Substitute x = -y.
.
-y +9 = 2y
9 = 3y
3y = 9
y = 3
.
x + y = 0
x + 3 = 0
x = -3
.
So the number is -3. its additive inverse is 3.
Twice the additive inverse = 2*(3) = 6.
-3 is indeed 9 less than 2*3.
.
Done.