A variation equation has a general form of:
[tex]y=mx[/tex]Where:
m= constant of variation
You have an especific point (2 , -5)
You can use this point to find the m (constant of variation), as follow:
x = 2
y = - 5
[tex]-5=m(2)[/tex][tex]m=-\frac{5}{2}[/tex]Now you can use the value of m to get the final equation:
[tex]y=-\frac{5}{2}x[/tex]