SOLUTION: Solve the following pairs of simultaneous equations: X+2y=3,X-2y=3 Y=2×-1,Y=3x-2 2y=6x-4,Y=3x-2

Algebra ->  Coordinate-system -> SOLUTION: Solve the following pairs of simultaneous equations: X+2y=3,X-2y=3 Y=2×-1,Y=3x-2 2y=6x-4,Y=3x-2      Log On


   



Question 1071223: Solve the following pairs of simultaneous equations:
X+2y=3,X-2y=3
Y=2×-1,Y=3x-2
2y=6x-4,Y=3x-2

Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
X+2y=3,X-2y=3
Y=2×-1,Y=3x-2
2y=6x-4,Y=3x-2
system%28X%2B2y=3%2CX-2y=3%29
system%28Y=2%D7-1%2CY=3x-2%29----This one is not rendering.
system%282y=6x-4%2CY=3x-2%29

-
Only doing one of your pair.
system%282y=6x-4%2Cy=3x-2%29

2%283x-2%29=6x-4
6x-4=6x-4
redundant.

Why?
2y=6x-4---first equation of the pair
2y%281%2F2%29=%286x-4%29%281%2F2%29
y=3x-2----same as second equation of the pair

The "pair" is really just one single equation in two different but equivalent forms. Solutions form the line.

Answer by ikleyn(52787) About Me  (Show Source):
You can put this solution on YOUR website!
.
Solve the following pairs of simultaneous equations:
X+2y=3,X-2y=3
Y=2×-1,Y=3x-2
2y=6x-4,Y=3x-2
~~~~~~~~~~~~~~~~~~~~~

1. 

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

Add the two equations (both sides). The terms with "y" will cancel, and you will get

2x = 6, which implies x = 3.

Now, substitute the found value x= 3 into the first equation. You will get

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

Answer. The solution is x= 3, y= 0.
        The method I applied is called the Elimination method.




2. 

y = 2x - 1,
y = 3x - 2.

Since the left sides are identical, the right sides are equal:

2x - 1 = 3x - 2  --->  -1 + 2 = 3x - 2x  --->  1 = x  --->  x = 1.

Now, substitute the found value x= 1 into the first equation. You will get

y = 2*1 - 1 = 2 - 1 = 1.

Answer.  The solution is x= 1, y= 1.




3.

2y = 6x - 4, 
 y = 3x - 2.

In the first equation, divide both sides by 2. You will get an equivalent equation

 y = 3x - 4.

Compare it with the second equation.
You see that they are identical.

So, your system is actually one equation for two unknowns, since the second equation is equivalent to the first one.

Geometrically, these two equations represent one straight line.

The original system has infinitely many solutions.


On solving systems of two linear equations in two unknowns see the lessons
    - Solution of the linear system of two equations in two unknowns by the Substitution method
    - Solution of the linear system of two equations in two unknowns by the Elimination method
    - Solution of the linear system of two equations in two unknowns using determinant
    - Geometric interpretation of the linear system of two equations in two unknowns
in this site.

Also, you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Systems of two linear equations in two unknowns".