Question 149527
Notice that "y" is nowhere to be seen in this equation. This means that y can be <font size=4><b>any</b></font> value while x <font size=4><b>must</b></font> be equal to 4. 


So let's plot the points (4,-5), (4,-4), (4,-3), (4,-2), (4,-1), (4,0), (4,1), (4,2), (4,3), (4,4), and (4,5)


Notice how <font size=4><b>all</b></font> of these points have the x coordinate 4 and y is any value.



{{{ drawing(500, 500, -10, 10, -10, 10,
 graph( 500, 500, -10, 10, -10, 10,0),
 circle(4,-5,0.08),
circle(4,-5,0.10),  circle(4,-4,0.08),
circle(4,-4,0.10),  circle(4,-3,0.08),
circle(4,-3,0.10),  circle(4,-2,0.08),
circle(4,-2,0.10),  circle(4,-1,0.08),
circle(4,-1,0.10),  circle(4,0,0.08),
circle(4,0,0.10),  circle(4,1,0.08),
circle(4,1,0.10),  circle(4,2,0.08),
circle(4,2,0.10),  circle(4,3,0.08),
circle(4,3,0.10),  circle(4,4,0.08),
circle(4,4,0.10),  circle(4,5,0.08),
circle(4,5,0.10)

)}}}



Now draw a line through these points to graph {{{x=4}}}




{{{ drawing(500, 500, -10, 10, -10, 10,
 graph( 500, 500, -10, 10, -10, 10,0),
 blue(line(4,-10,4,10)),
 circle(4,-5,0.08),
circle(4,-5,0.10),  circle(4,-4,0.08),
circle(4,-4,0.10),  circle(4,-3,0.08),
circle(4,-3,0.10),  circle(4,-2,0.08),
circle(4,-2,0.10),  circle(4,-1,0.08),
circle(4,-1,0.10),  circle(4,0,0.08),
circle(4,0,0.10),  circle(4,1,0.08),
circle(4,1,0.10),  circle(4,2,0.08),
circle(4,2,0.10),  circle(4,3,0.08),
circle(4,3,0.10),  circle(4,4,0.08),
circle(4,4,0.10),  circle(4,5,0.08),
circle(4,5,0.10)

)}}} Graph of {{{x=4}}}


So we can see that the line is a vertical line through {{{x=4}}}