[tex]x + 2y = 0[/tex]
[tex]x - y = 9[/tex]
Subtract the second equation from the first equation :
[tex](x + 2y) - (x - y) = 0 - 9[/tex]
[tex]x + 2y - x + y = - 9[/tex]
[tex]x - x + 2y + y = - 9[/tex]
Collect like terms
[tex]0 + 3y = - 9[/tex]
[tex]3y = - 9[/tex]
Divide both sides by 3
[tex] \frac{3y}{3} = \frac{ - 9}{3} \\ [/tex]
[tex]y = - 3[/tex]
Now it's time to find the value of x so put the y value in one of the above equations to find the value of x :
[tex]x = - 2 \times y[/tex]
[tex]x = - 2 \times ( - 3)[/tex]
[tex]x = 6[/tex]
Thus the solution is :
[tex]s = (6 \: , - 3)[/tex]
