SOLUTION: How do you solve {{{y=3x + 1}}} {{{ x=3y + 1}}}. Using substitution. Our teacher has given us this practice with no review from her. I don't know where to start using substitutio

Question 75916This question is from textbook Prentice Hall Algebra
: How do you solve . Using substitution. Our teacher has given us this practice with no review from her. I don't know where to start using substitution. This question is from textbook Prentice Hall Algebra

Found 2 solutions by ankor@dixie-net.com, scott8148:
Answer by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
How do you solve y = 3x + 1: x = 3y + 1. Using substitution.
:
y = (3x+1); than means that where you see "y" in the 2nd equation you can
substitute (3x+1) for y
:
The 2nd equation:
x = 3y + 1
:
Now substitute (3x+1) for y in the above equation:
x = 3(3x+1) + 1
:
Multiply what's inside the brackets and you have:
x = 9x + 3 + 1
x = 9x + 4
:
Subtract x from both sides, subtract 4 from both sides and you have:
-4 = 9x - x
-4 = 8x
x = -4/8
x = -1/2
:
Remember that y = (3x+1)
x = -1/2 so substitute -1/2 for x:
y = 3(-1/2) + 1
y = -3/2 + 1
y = -3/2 + 2/2
y = -1/2 also
:
Check our solutions by substituting for both x and y in the 2nd equation:
x = 3y + 1.
-1/2 = 3(-1/2) + 1
-1/2 = -3/2 + 2/2
-1/2 = -1/2; equality reigns
:
How about this? Make sense to you?
Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
substitution means taking a quantity from one equation and substituting its equivalent into another equation

In your case, taking the y from the first equation and substituting into the second equation gives x=3(3x+1)+1...every "y" in the second equation is replaced by its equivalent from the first equation "3x+1"... so x=9x+3+1...or x=-1/2

noting the symmetry of the two equations (they are identical, with the variables switched) means that y will also be -1/2. You could confirm this by practicing a substitution from the second equation to the first
RELATED QUESTIONS
my math teacher taught us how to do this but i don't understand (3,2), y = x + 5 (answered by josgarithmetic)
Please help with this question. This is my first homework for Geometry, I have had... (answered by Earlsdon)
hey there, I'm struggling with a bit of university pre calc this is an activity i... (answered by stanbon)
hey there, I'm struggling with a bit of university pre calc this is an activity i... (answered by stanbon)
Hi my name is jason and i dont have problems out of a text book but in a packet that my... (answered by Earlsdon)
How do I solve this system using the substitution method? x-y=3... (answered by Alan3354)
We are soing an Alg. 1 review to start off Alg. 2 and after 2 years i forgot almost... (answered by Earlsdon)
4x -12y =5 -x +3y = -1 how do you solve this using the substitution... (answered by MathLover1)
How do you solve this linear system by using substitution? x= 6-4y... (answered by jojo14344)