How do you graph y=-2/(x+3)-2 using asymptotes, intercepts, end behavior?

1 Answer
Sep 14, 2017

graph{-2/(x+3)-2 [-10, 10, -8, 8]}

Explanation:

I would advocate that just because we have more advanced mathematical skills , it does not mean that we should automatically use them in favour of basic translation skills.

We can write the given equation:

y = -2/(x+3)-2

In the form:

(y+2) = -2/((x+3))

We should now recognise this as the graph of the function

y=1/x

graph{1/x [-10, 10, -8, 8]}

Which is:

1) inverted to give y=-1/x
graph{-1/x [-10, 10, -8, 8]}

2) scaled by a factor of 2 to give y=-2/x
graph{-2/x [-10, 10, -8, 8]}

2) translated 3 units to the left to give y=-2/(x+3)
graph{-2/(x+3) [-10, 10, -8, 8]}

3) translated 2 units down to give (y+2)=-2/(x+3)
graph{-2/(x+3)-2 [-10, 10, -8, 8]}

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In the spirit of the question if we must use asymptotes, intercepts, end behavior then:

y = -2/(x+3)-2

End Behaviour:

x rarr +oo => x+3 rarr +oo => (-2)/(x+3) rarr 0^-
x rarr -oo => x+3 rarr -oo => (-2)/(x+3) rarr 0^+

Hence the end behaviour is as follows:

lim_(x rarr +oo) y = -2^- and lim_(x rarr -oo) y = -2^+

Asymptotes

The denominator is zero when x+3 = 0

Hence, we have a vertical asymptote at x=-3

Intercepts

When:

x=0 => y = 2/3-2 = -4/3
y=0 => -1/(x+3)=1 => x=-4

Hence, the intercepts are (0,-4/3) and (-4,0)

Which is enough the sketch the curve.