- Data Structure
- Networking
- RDBMS
- Operating System
- Java
- MS Excel
- iOS
- HTML
- CSS
- Android
- Python
- C Programming
- C++
- C#
- MongoDB
- MySQL
- Javascript
- PHP
- Physics
- Chemistry
- Biology
- Mathematics
- English
- Economics
- Psychology
- Social Studies
- Fashion Studies
- Legal Studies
- Selected Reading
- UPSC IAS Exams Notes
- Developer's Best Practices
- Questions and Answers
- Effective Resume Writing
- HR Interview Questions
- Computer Glossary
- Who is Who
Without actually calculating the cubes, find the value of each of the following:
(i) $ (-12)^{3}+(7)^{3}+(5)^{3} $
(ii) $ (28)^{3}+(-15)^{3}+(-13)^{3} $
To do:
We have to find the values of each of the given expressions.
Solution:
We know that,$x^{3}+y^{3}+z^{3}-3xyz=(x+y+z)(x^{2}+y^{2}+z^{2}-xy-yz-zx)$
If $x+y+z =0$, then
$x^{3}+y^{3}+z^{3}-3xyz= (0)(x^{2}+y^{2}+z^{2}-xy-yz-zx)$
$x^{3}+y^{3}+z^{3}-3xyz=0$
$x^{3}+y^{3}+z^{3}=3xyz$
(i) \( (-12)^{3}+(7)^{3}+(5)^{3} \)
Here,
$a=-12, b=7, c=5$
This implies,
$a+b+c=-12+7+5$
$=-12+12$
$=0$
Therefore,
$(-12)^{3}+(7)^{3}+(5)^{3}=3(-12)(7)(5)$
$=-36\times35$
$=-1260$
(ii) \( (28)^{3}+(-15)^{3}+(-13)^{3} \)
$a=28, b=-15, c=-13$
This implies,
$a+b+c=28+(-15)+(-13)$
$=28-(15+13)$
$=28-28$
$=0$
Therefore,
$(28)^{3}+(-15)^{3}+(-13)^{3}=3(28)(-15)(-13)$
$=84\times195$
$=16380$
Advertisements
To Continue Learning Please Login
Login with Google