SOLUTION: hi, i need to solve this using elimination method and check 15x+3y=-12 2x+y=8

Question 147695This question is from textbook
: hi, i need to solve this using elimination method and check
15x+3y=-12
2x+y=8 This question is from textbook

Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!

Start with the given system of equations:

Multiply the both sides of the second equation by -3.

Distribute and multiply.

So we have the new system of equations:

Now add the equations together. You can do this by simply adding the two left sides and the two right sides separately like this:

Group like terms.

Combine like terms. Notice how the y terms cancel out.

Simplify.

Divide both sides by to isolate .

Reduce.

------------------------------------------------------------------

Now go back to the first equation.

Plug in .

Multiply.

Add to both sides.

Combine like terms on the right side.

Divide both sides by to isolate .

Reduce.

So our answer is and .

Which form the ordered pair

.

This means that the system is consistent and independent.

Notice when we graph the equations, we see that they intersect at

. So this visually verifies our answer.

Graph of (red) and (green)

---------------------------
Check:

Start with the first equation.

Plug in and .

Evaluate and simplify the left side.

Since the equation is true, this means that (-4,16) is a solution of the first equation

-------------

Start with the second equation.

Plug in and .

Evaluate and simplify the left side.

Since the equation is true, this means that (-4,16) is a solution of the second equation.

Since all of the equations of the system are true, this means that (-4,16) is a solution to the system. So this verifies our answer.
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