Original
Find the slant asymptote of
{{MATH_46}}
{{CMD_47}}
We are looking to see if there is a line {{MATH_48}} such that
{{MATH_49}}
First, let's consider the limit as {{MATH_50}} approaches positive infinity. We will imagine that we have such a line
{{MATH_51}}
and attempt to find the correct values for {{MATH_52}} and {{MATH_53}}. Let's look again at our limit. We are assuming:
{{MATH_54}}
We know that {{MATH_55}} is continuous everywhere except at {{MATH_56}} and {{MATH_57}} is continuous everywhere, so
we can apply our limit laws away from {{MATH_58}}. We're looking at large values of {{MATH_59}}, so this is no problem. We use the fact that the sum of the limits is the limit of the sums.
{{ENV_60}}
We are assuming these two limits are equal. Dividing by {{MATH_61}} on the right hand side makes the limit equal to {{MATH_62}}:
{{ENV_63}}
To find the value of {{MATH_64}}, then, we can divide the left hand side by {{MATH_65}} and evaluate the limit. We see the following.
{{ENV_66}}
So {{MATH_67}}. We now know that
{{MATH_68}}
for some value of {{MATH_69}}. To find the {{MATH_70}}-intercept {{MATH_71}}, we use a similar method. Notice that
{{MATH_72}}
so if we subtract {{MATH_73}} from the right hand side, we are left with just {{MATH_74}}. Since the two sides are equal, subtracting {{MATH_75}} from the left hand side and evaluating the limit will give us the value for {{MATH_76}}. We write the following.
{{ENV_77}}
By this method, we have determined that
{{MATH_78}}
In other words, {{MATH_79}} is a slant asymptote
for our function {{MATH_80}}. You should check that we get the same slant
asymptote {{MATH_81}} when we take the limit to
negative infinity as well.
{{CMD_82}}
We can confirm our results by looking at the graph of {{MATH_83}}
and {{MATH_84}}:
{{MATH_85}}
{{CMD_86}}
{{CMD_87}}
{{CMD_88}}