SOLUTION: I need to solve by addition: 5x-4y=9 and -x+2y=3. I know I need to multiply the first two coefficients by 5, but they both come up as -5. Is there any solution or is there no solut

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: I need to solve by addition: 5x-4y=9 and -x+2y=3. I know I need to multiply the first two coefficients by 5, but they both come up as -5. Is there any solution or is there no solut      Log On


   

Question 561290: I need to solve by addition: 5x-4y=9 and -x+2y=3. I know I need to multiply the first two coefficients by 5, but they both come up as -5. Is there any solution or is there no solution because it is dependent?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
(1) +5x+-+4y+=+9+
(2) +-x+%2B+2y+=+3+
Just leave (1) alone and multiply both sides of (2)
by +2+
If you do the same thing to both sides, the equation is still true
(2) +-2x+%2B+4y+=+6+ is the result
Now just add the equations
(1) +5x+-+4y+=+9+
(2) +-2x+%2B+4y+=+6+
+3x+=+15+
+x+=+5+
Plug this value back into (2)
(2) +-5+%2B+2y+=+3+
(2) +2y+=+3+%2B+5+
(2) +2y+=+8+
(2) +y+=+4+
The solution is (5,4)