How do you graph f(x)=(x-2)/(x-4) using holes, vertical and horizontal asymptotes, x and y intercepts?

1 Answer
Jan 25, 2018

Undefined at x=4
See explanation for the rest

Explanation:

color(blue)("Hole - undefined")

Hole is where the denominator becomes 0. The function becomes undefined at that point. So for this condition we have x=4

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Lets consider the behaviour close to x=4

color(blue)("Vertical Asymptot "->+oo)

If x=4+delta4 where delta4>0 and very small then we have

(4+delta4-2)/(cancel(4)+delta4-cancel(4)) ->2/(delta4)+1

lim_(delta4->color(white)()^+ 0)2/(delta4)+1 color(white)("dd")->color(white)("dd")kcolor(white)("dd")->color(white)("dd")+oo+1=+oo

color(blue)("Vertical Asymptot "->-oo)

If x=4-delta4 where delta4>0 and very small then we have

(4-delta4-2)/(cancel(4)-delta4-cancel(4)) ->(2-delta4)/(-delta4)=-2/(delta4)+1

lim_(delta4->color(white)()^+ 0)-2/(delta4)+1color(white)("dd") ->color(white)("dd")kcolor(white)("dd")->color(white)("dd")-oo+1=-oo
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
color(blue)("Horizontal Asymptot "->+oo)

(x-2)/(x-4)

As x>0 becomes increasing greater and greater the influences of the -2 and -4 become less and less significant. This continues until we have

lim_(x->+oo) (x-2)/(x-4)color(white)("dd")->color(white)("dd")kcolor(white)("dd") ->color(white)("dd")oo/oo=+1

As x<0 becomes increasing less and less the influences of the -2 and -4 become less and less significant. This continues until we have

lim_(x->-oo) (x-2)/(x-4)color(white)("dd")->color(white)("dd")kcolor(white)("dd") ->color(white)("dd")(-oo)/(-oo)=+1

Tony B