SOLUTION: y=2x+5 3x-y=4 page 69 algebra review

Question 101732: y=2x+5
3x-y=4
page 69 algebra review
Answer by doukungfoo(195) (Show Source): You can put this solution on YOUR website!
There are three ways to solve systems of equations with two variables.
They are
1. Substitution Method
2. Elimination Method
3. Graphing
For this problem I will demonstrate the substitution method.
Ok so we are working with two equations:
y = 2x + 5
3x - y = 4
The first equation shows that 2x+5 equals y So we are going to take 2x+5 and substitute it for y in the second equation. So you can see that is why this is called the substitution method.
ok we have
3x - y = 4
now substitute y with 2x+5
3x - (2x + 5) = 4
now we can solve for x
first distribute the negative sign across (2x + 5)
3x - 2x - 5 = 4
next combine like terms
x - 5 = 4
now solve for x by adding 5 to both sides
x = 9
ok we found our first variable x = 9
now use this value for x and substitute it in the first equation.
and solve for y
y = 2x + 5
y = 2(9) + 5
y = 18 + 5
y = 23
now we have found the second variable y = 23
All that is left to do is check our answers.
y = 2x + 5
23 = 2(9) + 5
23 = 18 + 5
23 = 23
now check the answers in the second equation
3x - y = 4
3(9) - 23 = 4
27 - 23 = 4
4 = 4
So the answers we got work for both equations.
Thats it.

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