Math Systems
posted by Sam on .
I cannot solve these last three systems. Could you show me the work for them so i understand how to do them.
1)
xy=1
2x+y=5
3x4y=2
2)
5x+8y+6z=14
2x+5y+z=12
3x+6y12z=20
3)
x^2+2xy2y^2=11
x^2+xy2y^2=9

problem 1
in the equation x  y = 1, solve for x in terms of y.
replace x in either of the other two equations and you will be able to solve for x. Now, you can go back to any of the three equations and replace x with the value you found and solve for y.
Check that your solution for x and y satisfy all three equations. 
1)
xy=1
x = 1 + y
2x+y=5
2(1 + y) + y = 5
2 + 2y + y = 5
3y = 3
y = 1
3x4y=2
3x  4 = 2
3x = 6
x = 2