SOLUTION: A.Can you please give me an example of a system of equations that is more easily solved by substitution? B. Can you give me an example of a system of equations that is more easi

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Question 107814: A.Can you please give me an example of a system of equations that is more easily solved by substitution?
B. Can you give me an example of a system of equations that is more easily to solve by addition?
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!
1.
Solve by adding:
-3x+%2B+5y+=+12
3x+%2B+2y+=+9



If we add the two equations, we will get 0x+%2B+7y+=+21 or 7y+=+21.
If we divide both sides by 7, we get y+=+3.
Next, we substitute 3 in for y into any of given equations.
If we choose to substitute in the first equation, we get+-3x+%2B+5%283%29+=+12… ==> …-3x+%2B+15+=+12+…==>… +-3x+=+-3… ==>… x+=+1.
So the two lines intersect at (1, 3).


2.
Solve a system by substitution
1st: Pick 1 equation and solve for 1 of the variables.

5x%2B4y=6
y+=-2x%2B3+

The second equation is already solved for y.

"-2x%2B3" is the expression needed.

2nd: Substitute this expression in the other equation.
5x%2B4y+=+6
5x+%2B+4%28-2x+%2B+3%29+=+6

3rd: Sovle.
5x%2B4%28-2x%2B3%29=+6
5x-8x%2B12=+6
-3x%2B12=+6
Add -12 to the both sides
-3x%2B12+%96+12+=+6+-+12
-3x=++-+6……..divide both sides by -3
-3x%2F%28-3%29+=+-6%2F%28-3%29
x+=+2


4th: Use this new value in the step 1 equation to get the other variable.
y+=-2x%2B3+
y+=-2%2A2+%2B+3+
y+=+-+4+%2B+3+
y+=+-+1


5th: State the solution and include values for both variables.
x+=+2
+y+=+-1+

So the two lines intersect at (2,-1)