Steply

Limit as x -> 0 of (x^2 + 2)/(x + 1) using L'Hôpital's rule

Step by step, with the reason for every step · L'Hôpital's rule · Calculus 1

Step by step

The question

Question: find the limit as x → 0 of (x² + 2)/(x + 1).

lim x → 0 x2 + 2x + 1 =

1 Put the number in

Put 0 in place of x.

The top is 2, and the bottom is 1.

The bottom is not 0, so there is no problem here.

top: 02 + 2 = 2
bottom: 0 + 1 = 1

Careful!

L'Hôpital's rule is only for 0/0, or infinity over infinity.

Here it would give 0, which is wrong.

Careful: not L'Hôpital: f′g′ → 0 ✗

So the limit is just the value: 2.

lim x → 0 x2 + 2x + 1 = 21 = 2

2 Check

Let's check with a calculator, with x very close to 0.

x = −0.01 gives about 2.0203.

x = −0.01: x2 + 2x + 1 ≈ 2.0203

And x = 0.01 gives about 1.9803.

Both are close to 2.

Right!

x = 0.01: x2 + 2x + 1 ≈ 1.9803

Let's look back.

First: put the number in.

Last: check.

Answer
lim x → 0 x2 + 2x + 1 = 21 = 2

Your turn

Try this one yourself, then check:

lim x → 3 x2 + 12x + 4
Show the answer
3

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