Question

solution to 3x+y=4 and x+y=0

Answer 1

x + y = 0 --> x = 0 - y
now sub 0 - y in for x in the first equation...
3x + y = 4
3(0 - y) + y = 4
0 - 3y + y = 4
-2y = 4
y = - 2
now sub -2 in for y in either of the original equations
x + y = 0
x + (-2) = 0
x - 2 = 0
x = 0 + 2
x = 2
check...
x + y = 0
2 + (-2) = 0
2 - 2 = 0
0 = 0 (correct)
or check with the other equation
3x + y = 4
3(2) + (-2) = 4
6 - 2 = 4
4 = 4 (correct)
ANSWER: x = 2 and y = -2 or (2,-2)