Definite Integral 2

Calculus Level 4

Evaluate

5050 × 0 1 ( 1 x 50 ) 100 d x 0 1 ( 1 x 50 ) 101 d x 5050 \times \frac{\displaystyle \int_{0}^{1}(1-x^{50})^{100}dx}{\displaystyle \int_{0}^{1}(1-x^{50})^{101}dx}

This problem is a part of my set Some JEE problems


The answer is 5051.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

2 solutions

Prakhar Gupta
Mar 19, 2015

Let's do it by Reduction Formula.

We can see it as the special case of the following integral. I n = 0 1 ( 1 x 50 ) n d x I_{n} = \int_{0}^{1} (1-x^{50})^{n}dx We can apply by parts in it. I n = [ x × ( 1 x 50 ) n ) ] 0 1 0 1 x × n ( 1 x 50 ) n 1 ( 50 x 49 ) d x I_{n} = \big[x\times (1-x^{50})^{n})\big]_{0}^{1}-\int_{0}^{1}x\times n(1-x^{50})^{n-1} (-50x^{49})dx I n = 50 n 0 1 x 50 ( 1 x 50 ) n 1 d x I_{n} = 50n\int_{0}^{1}x^{50}(1-x^{50})^{n-1}dx I n = 50 n ( 0 1 ( 1 x 50 ) n 1 d x 0 1 ( 1 x 50 ) n ) I_{n} = 50n\Big( \int_{0}^{1} (1-x^{50})^{n-1} dx - \int_{0}^{1}(1-x^{50})^{n}\Big) I n = 50 n I n 1 50 n I n I_{n} = 50nI_{n-1} - 50nI_{n} ( 1 + 50 n ) I n = 50 n I n 1 (1+50n) I_{n} = 50n I_{n-1} I n 1 I n = 1 + 50 n 50 n \dfrac{I_{n-1}}{I_{n}} = \dfrac{1+50n}{50n} Put n = 101 n = 101 to get the required answer.

Kartik Sharma
Mar 5, 2015

Use Beta function!

it can also be solved using ilate rule.

Tanishq Varshney - 6 years, 3 months ago

Log in to reply

Nice question @Tanishq Varshney . I used beta function to solve it. Where did u get the question?

Aditya Kumar - 6 years ago

Log in to reply

JEE 2006 or 2005

Tanishq Varshney - 6 years ago

Log in to reply

@Tanishq Varshney Hmm...thanks! U there on G+??

Aditya Kumar - 6 years ago

Log in to reply

@Aditya Kumar Nope , :C

Tanishq Varshney - 6 years ago

By using B E T A F U N C T I O N BETA - FUNCTION it will to0 l e n g t h y lengthy

harsh soni - 6 years, 2 months ago

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...