SOLUTION: Solve the system & identify it as consistent, inconsistent or dependent. { 4x+y=8 4x+5y=-8 } a) (3,-4); consistent/dependent b) {(3,-4) l 4x+y=8}; consistent/dependent

Question 151524: Solve the system & identify it as consistent, inconsistent or dependent.
{ 4x+y=8
4x+5y=-8 }
a) (3,-4); consistent/dependent
b) {(3,-4) l 4x+y=8}; consistent/dependent
c) 0; inconsistent
d) (3,-4); consistent/independent
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 -1.

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 x 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.

So the answer is choice d) (3,-4); consistent/independent

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

. So this visually verifies our answer.

Graph of (red) and (green)

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