Evaluate the limit of \(\displaystyle\lim_{{{x}\to\infty}}{\frac{{{x}-\sqrt{{{x}^{{2}}+{5}{x}+{2}}}}}{{{x}-\sqrt{{{x}^{{2}}+{0.5}{x}+{1}}}}}}\)

Pablo Dennis

Pablo Dennis

Answered question

2022-04-05

Evaluate the limit of
limxxx2+5x+2xx2+0.5x+1

Answer & Explanation

microsgopx6z7

microsgopx6z7

Beginner2022-04-06Added 14 answers

We give two solutions. The first uses a standard trick that you have probably already seen. The second uses the definition of the derivative.
You are familiar with the identity
(uv)(u+v)=uv,  ()
at least in its incarnation (ab)(a+b)=a2b2. We will use () twice. First, we multiply the top and bottom of your expression by
(x+x2+5x+2)(x+x2+0.5x+1)
We get
xx2+5x+2xx2+0.5x+1=(xx2+5x+2)(x+x2+5x+2)(x+x2+0.5x+1)(xx2+0.5x+1)(x+x2+0.5x+1)(x+x2+5x+2)
The product of the first two terms on top is (5x+2), and the product of the first two terms at the bottom is (0.5x+1). It follows that
(5x+2)(x+x2+0.5x+1)(0.5x+1)(x+x2+5x+2)=(5+2x)(1+1+0.5x+1x2)(0.5+1x)(1+1+5x+2x2).        (***)
If we look at the right-hand side of (***), it should be clear that as x, the top approaches 10 and the bottom approaches 1.

Do you have a similar question?

Recalculate according to your conditions!

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?