Is x1+x2=x3+x4 a linear equation?

[hivesaeed4]

Is it? Personally, I think it is since the max power on any unknown is 1, no trig function, no product of unknowns etc. Also could the above mentioned linear equation form a linear system ? I don't think so (cause we always need at least two separate linear equations to form a linear system) but I just want to be sure.

 

[Studiot]

Please note that 'a linear equation', 'the equation of a straight line' and 'a linear system' are three different things.

Your sample equation is a linear equation.

It is not the equation of a straight line.

It could even be part of a linear system, but by itself is not enough to form one since there are four variables mentioned.