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JEE Main Syllabus 2025 (Physics, Chemistry, Maths)- Download PDF Here

Problems on Divisibility - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #JEE Main

Quick Facts

  • 13 Questions around this concept.

Solve by difficulty

The number 101^{100}-1 is divisible by 

For every natural number  n, 3^{2 n+2}-8 n-9  is divisible by:

(1+x)^n-n x-1  is divisible by (where n \in N ):

 

The greatest integer, which divides the number  (101^{100}-1) is

49^n+16 n-1 is divisible by:

The difference between an integer and its cube is divisible by    

Concepts Covered - 2

Problems on Divisibility

Given Expression is divisible by an Integer

\\\mathrm{1.\;\;Expression,\;(1+x)^n-1\;is\;divisible\;by\;x\;because}\\\mathrm{\;\;\;\;\;(1+x)^n-1= \;(^n C_0\;+\;^nC_1x\;+\;^nC_2x^2+......+^nC_nx^n)-1}\\\mathrm{\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;=x\left [ \;\;^nC_1\;+\;^nC_2x+......+^nC_nx^{n-1} \right ]}\\\mathrm{2.\;\;Expression,\;(1+x)^n-nx-1\;is\;divisible\;by\;x^2\;because}\\\mathrm{\;\;\;\;\;(1+x)^n-nx-1= \;(^n C_0\;+\;^nC_1x\;+\;^nC_2x^2+......+^nC_nx^n)-nx-1}\\\mathrm{\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;\;=x^2\left [ \;\;^nC_2+\;^nC_3x+......+^nC_nx^{n-2} \right ]}


 

For example: 

\\Prove\,\,that\,\,3^{2 n+2}-8 n-9 \text { is divisible by } 8 \text { if } n \in N \\\\ \begin{array}{l}{\begin{aligned} 3^{2 n+2} &-8 n-9=(1+8)^{n+1}-8 n-9 \\ &=\left[1+(n+1) 8+^{n+1} C_{2} 8^{2}+\ldots\right]-8 n-9 \\ &=^{n+1} C_{2} 8^{2}+^{n+1} C_{3} 8^{3}+^{n+1} C_{4} 8^{4}+\ldots \\ &=8\left[^{n+1} C_{2}8+^{n+1} C_{3} 8^2+^{n+1} C_{4} 8^{3}+\ldots .\right] \end{aligned}} \\ {\text { which is clearly divisible by } 8 .}\end{array}

Some standard results of Divisibility Problem

Divisibility: Important Results

  1. The expression \mathrm{a^n-b^n} is divisible by \mathrm{a+b}, if \mathrm{n} is even.

  2. The expression \mathrm{a^n-b^n} is divisible by \mathrm{a-b}, if n is even or odd.

  3. The expression \mathrm{a^n+b^n} is divisible by , \mathrm{a+b} if n is odd.

In all the above cases n is a natural numbers.

For Example

The expression \mathrm{15^4-7^4} is divisible by (15+7)=22 \text { and }(15-7)=8.

Study it with Videos

Problems on Divisibility
Some standard results of Divisibility Problem

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