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Home Q & A Board Science-Related Homework Help Mathematics
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buggingout16 buggingout16
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Posts: 96
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11 years ago
The equations are:
x = 2y + 3
y = x

The answer is (-3, -3)
But I have no clue how they got it. I have to use the substitution method, not addition method.
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6 Replies
Replies
wrote...
#1
11 years ago
Flip the second equation around to make it a little easier for yourself.

x = 2y + 3
x = y

We know that x is equal to y and that x is also equal to 2y + 3.  2y + 3 = y must also be true.

2y + 3 = y
y = -3

Now plug y = -3 into either equation.
x = 2(-3) + 3
x = -3
wrote...
#2
11 years ago
x = 2y+3
-x = -y

Add the above equations gives you 0=y+3  Which yields y= -3

Since x=y, x= -3
Answer accepted by topic starter
NVWolfNVWolf
wrote...
#3
Posts: 18
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11 years ago
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#4
11 years ago
Substitute y for x (from 2nd equation.

y = 2y + 3

- y = 3

y = -3

x = -3

Proof: - 3 = - 6 + 3 or -3.
wrote...
#5
11 years ago
x = 2y + 3
x = y

x =  2x + 3........0 = 2x - x + 3........0 = x + 3.......- 3 = x = y

x = 2x + 3.......- 3 = 2x - x ......- 3 = x

Subtract x = y from x = 2y + 3:

x = 2y + 3
x = y
___________
0 = y + 3............- y = 3 OR - 3 = y......- ( - 3 ) = 3
wrote...
#6
11 years ago
Use substitution method...

x = 2x + 3
-x = 3
x = -3

So since y = x = -3, the solution is (-3,-3)

I hope this helps!
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