SOLUTION: why x=4 is not a function of a linear equation?

Question 372597: why x=4 is not a function of a linear equation?
Answer by Jk22(389) (Show Source): You can put this solution on YOUR website!
Normally linear function are straight lines passing at the origin (0,0)

linear function in 2d are of the form y=ax, more generally : ax+by=0 is the equation of a linear function.

x=4 is the equation of a vertical line passing at x=4.

We have that the sum of 2 linear function should be linear again, let suppose

ax+by = 0 one of those, then adding with x=4 gives :

(a+1)x+by = 4.

this 4 makes that x=4 is not the equation of a linear function.

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