Posted by please help!!! on Tuesday, January 18, 2011 at 10:53pm.
i don't get these please help me:
use the subtitution method to solve the linear system
1)3x+y=0 xy=4
2)y=3x1 x3y=3
3)3xy=9 2x+y=6
4)x2y=0 3x+y=0
Thank you!!:)

math(algebra 1)  helper, Tuesday, January 18, 2011 at 11:17pm
1)3x + y = 0, x  y = 4
Pick and equation, and solve for either x or y
x  y = 4
x = 4 + y
Substitute, x = 4 + y, for x, in the other equation and solve for y
x = 4 + y
3x + y = 0
3(4 + y) + y = 0
12 + 3y + y = 0
12 + 4y = 0
4y = 12
y = 3
substitute y = 3 in either equation to find x
x  y = 4
x  (3) = 4
x + 3 = 4
x = 1
Now you try the others 
math(algebra 1)  please help!!, Tuesday, January 18, 2011 at 11:47pm
so are these correct?
2)y=3x1 x3y=3
x=0 y=1???
3)3xy=9 2x+y=6
dont know help??
4)x2y=0 3x+y=0
please help!!! i don't know how you changed x  y = 4 to x = 4 + y tell me please
Thanks!! 
math(algebra 1)  helper, Wednesday, January 19, 2011 at 12:57pm
2) you are correct
x  y = 4
add + y to both sides
x  y + y = 4 + y
x = 4 + y