Are the given lines perpendicular?

y=6 , x=6

give a reason why or why not : ).
*will give brainliest*

The number of pages in the u.s. tax code exceeds the number of pages in the king james bible by 18,528. the combined number of pages in the tax code and the bible is 21,472

Kylie explained that (-4x+9)^2 will result in a difference of squares because (-4x+9)^2 (-4x+9)^2 =(-4x)^2+(9)^2=16x^2+81

Aclassmate thinks that solving a system by graphing gives an exact answer when the lines appear to cross at a grid point, but only an approximate answer when they don't. explain why this isn't true.