Theorem, from definition of derivative, Mathematics

Assignment Help:

Theorem, from Definition of Derivative

 If f(x) is differentiable at x = a then f(x) is continuous at x =a.

Proof : Since f(x) is differentiable at x = a we know,

f'(a) = lim x→a (f(x) - f(a))/(x - a)

exists. We will require this in some.

 If we next suppose that x ≠ a we can write the as given below,

f(x) - f(a) = ((f(x) - f(a))/( x -a)) (x -a)

Afterward fundamental properties of limits tells us as we have,

lim x→a (f(x) - f(a)) = lim x→a [((f(x) - f(a))/(x - a)) (x -a)]

= lim x→a (f(x) - f(a))/(x - a) lim x→a (x -a)

The primary limit on the right is only f′(a) as we considered above and the second limit is obviously zero and therefore,

lim x→a (f(x) - f(a)) = f'(a).0 = 0

So we've managed to prove as,

lim x→a (f(x) - f(a)) = 0

Although just how does this help us to x= a, prove that f(x) is continuous at x = a?

 Let's establish with the subsequent.

lim x→a (f(x)) = lim x→a [f(x) + f(a) - f(a)]

Remember that we have just added in zero upon the right side. Some rewriting and the utilize of limit properties provides,

limx→a (f(x)) = limx→a [f(a) + f(x) - f(a)]

= limx→a f(a) + limx→a [f(x) - f(a)]

Here, we only proved above that limx→a [f(x) - f(a)] = 0 and since f(a) is a constant we also know that limx→a f(a) = f(a), then it should be,

limx→a f(x) = limx→a f(a) = 0 = f(a)

Or conversely, limx→a f(x) = f(a) although it is exactly what this means for f(x) is continuous at x = a and therefore we are done.


Related Discussions:- Theorem, from definition of derivative

Tangents, two circle of radius of 2cm &3cm &diameter of 8cm dram common tan...

two circle of radius of 2cm &3cm &diameter of 8cm dram common tangent

Estimates the probabilities of price changes, Mr. Hoper is in charge of inv...

Mr. Hoper is in charge of investments for the golden horizon company. He estimates from past price fluctuations in the gold market that the probabilities of price changes on a give

Quantitative method, Year 1 2 3 4 ...

Year 1 2 3 4 5 6 7 8 9 10 Corn revenue 40 44 46

Show that the angles subtended at the centre , A circle touches the sides o...

A circle touches the sides of a quadrilateral ABCD at P, Q, R and S respectively. Show that the angles subtended at the centre by a pair of opposite sides are supplementary.

Determine the number of full withdrawals, A worker retires with a lump sum ...

A worker retires with a lump sum superannuation benefit of $500,000. She immediately invests this money in a fund earning 5% pa effective. One year after retirement she begins maki

Julie had $500 how much money did julie spend, Julie had $500. She spent 20...

Julie had $500. She spent 20% of it on clothes and then 25% of the remaining money on CDs. How much money did Julie spend? Find out 20% of $500 by multiplying $500 by the decim

Polynomials in two variables, Polynomials in two variables Let's take a...

Polynomials in two variables Let's take a look at polynomials in two variables.  Polynomials in two variables are algebraic expressions containing terms in the form ax n y m

Function notation, Function notation: Next we have to take a rapid look at...

Function notation: Next we have to take a rapid look at function notation. Function notation is nothing more than way of writing the y in a function which will let to simplify not

Class limits and class boundries, Class limits These are numerical va...

Class limits These are numerical values, which limits uq extended of a given class that is all the observations in a provided class are expected to fall in the interval which

Analysis of algorithm running time - undirected graph, Problem. You are giv...

Problem. You are given an undirected graph G = (V,E) in which the edge weights are highly restricted. In particular, each edge has a positive integer weight of either {1, 2, . .

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd