5x+7y= 1
4x-2y=16
2007-01-01 10:48:00 · 2 answers · asked by eduardo r 1 in Science & Mathematics ➔ Mathematics
5x + 7y = 1
4x - 2y = 16
Reduce the second equation.
5x + 7y = 1
2x - y = 8
2x - y = 8 means y = 2x - 8. Plug this value of y into the first equation, to obtain
5x + 7(2x - 8) = 1
5x + 14x - 56 = 1
19x = 57
x = 3
Plug x = 3 into the second equation to get 5(3) + 7y = 1, or
15 + 7y = 1, 7y = -14, y = -2
x = 3, y = -2
2007-01-01 10:52:12 · answer #1 · answered by Puggy 7 · 0⤊ 0⤋
Dividing the second equation by 2, you get:
(4x - 2y)/2 = 16/2
2x - y = 8
Now, multiply that by 7 to get:
7(2x - y) = 7(8)
14x - 7y = 56
Add this equation to the first equation so:
5x + 7y = 1
+ 14x - 7y = 56
Summing the two equations gets: 19x = 57 so x = 3
You can plug in x = 3 back into the second given equation and you get:
4*3 - 2y = 16
-2y = 4
y = -2
Hope that helps!
2007-01-01 19:28:18 · answer #2 · answered by S S 2 · 0⤊ 0⤋