SOLUTION: Alright the question is 4x+y=-9 4x+2y=-10 My answer 4x+y=-9 4x+2y=-10 3y= -19 so i divided -19 by 3 and got 6.3 but my answer was wrong. I dont know what i did wrong here

Algebra ->  Coordinate Systems and Linear Equations -> SOLUTION: Alright the question is 4x+y=-9 4x+2y=-10 My answer 4x+y=-9 4x+2y=-10 3y= -19 so i divided -19 by 3 and got 6.3 but my answer was wrong. I dont know what i did wrong here      Log On


   

Question 322474: Alright the question is
4x+y=-9
4x+2y=-10
My answer
4x+y=-9
4x+2y=-10
3y= -19 so i divided -19 by 3 and got 6.3 but my answer was wrong. I dont know what i did wrong here.
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

Start with the given system of equations:
system%284x%2By=-9%2C4x%2B2y=-10%29


-2%284x%2By%29=-2%28-9%29 Multiply the both sides of the first equation by -2.


-8x-2y=18 Distribute and multiply.


So we have the new system of equations:
system%28-8x-2y=18%2C4x%2B2y=-10%29


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


%28-8x-2y%29%2B%284x%2B2y%29=%2818%29%2B%28-10%29


%28-8x%2B4x%29%2B%28-2y%2B2y%29=18%2B-10 Group like terms.


-4x%2B0y=8 Combine like terms.


-4x=8 Simplify.


x=%288%29%2F%28-4%29 Divide both sides by -4 to isolate x.


x=-2 Reduce.


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


-8x-2y=18 Now go back to the first equation.


-8%28-2%29-2y=18 Plug in x=-2.


16-2y=18 Multiply.


-2y=18-16 Subtract 16 from both sides.


-2y=2 Combine like terms on the right side.


y=%282%29%2F%28-2%29 Divide both sides by -2 to isolate y.


y=-1 Reduce.


So the solutions are x=-2 and y=-1.


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 4x%2By=-9 (red) and 4x%2B2y=-10 (green)