You can
put this solution on YOUR website!Yes it is because the power of the variables ( x and y ) is one. If you had an equation which contained

or

then the equation would not be linear, because the power of the variables is higher than 1 and if you were to graph it, your graph would not look like a line. The best way to differentiate is the formula for linear equations, which is

ie

. If your equation looks like the above then you have a lindear equation.
Good Luck!
PS I tutor in Rapid City, South Dakota area. For lessons please contact me.