SOLUTION: I am hoping you can help me with this one, I think I got the right answer, but my grade is falling rapidly and I need to check to see if it is right so that I don't make silly mist

Algebra ->  Coordinate Systems and Linear Equations -> SOLUTION: I am hoping you can help me with this one, I think I got the right answer, but my grade is falling rapidly and I need to check to see if it is right so that I don't make silly mist      Log On


   

Question 125976: I am hoping you can help me with this one, I think I got the right answer, but my grade is falling rapidly and I need to check to see if it is right so that I don't make silly mistakes that cost me.
The question is from a worksheet:
Solve the system by substitution
2x+2y=0
y=4x +0
I came up with y=4x
Is this even close. I am paranoid now about the answers I get so I just want to make sure I am doing them right. Thanks so much.
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

Start with the given system
2x%2B2y=0
y=4x%2B0



2x%2B2%284x%2B0%29=0 Plug in y=4x%2B0 into the first equation. In other words, replace each y with 4x%2B0. Notice we've eliminated the y variables. So we now have a simple equation with one unknown.


2x%2B8x%2B0=0 Distribute


10x%2B0=0 Combine like terms on the left side


10x=0-0Subtract 0 from both sides


10x=-0 Combine like terms on the right side


x=%28-0%29%2F%2810%29 Divide both sides by 10 to isolate x



x=0 Divide




Now that we know that x=0, we can plug this into y=4x%2B0 to find y



y=4%280%29%2B0 Substitute 0 for each x


y=0 Simplify


So our answer is x=0 and y=0 which also looks like



Notice if we graph the two equations, we can see that their intersection is at . So this verifies our answer.


+graph%28+500%2C+500%2C+-5%2C+5%2C+-5%2C+5%2C+-x%2C+4x%29+ Graph of 2x%2B2y=0 (red) and y=4x%2B0 (green)