LIVE Course for free

Rated by 1 million+ students
Get app now
JEE MAIN 2023
JEE MAIN 2023 TEST SERIES
NEET 2023 TEST SERIES
NEET 2023
CLASS 12 FOUNDATION COURSE
CLASS 10 FOUNDATION COURSE
CLASS 9 FOUNDATION COURSE
CLASS 8 FOUNDATION COURSE
0 votes
84 views
in Aptitude by (30.0k points)
closed by
If x4 + x-4 = 1154 then the value of x + x-1 is:
1. 5
2. 12
3. 6
4. 8

1 Answer

0 votes
by (30.0k points)
selected by
 
Best answer
Correct Answer - Option 3 : 6

Given:

 x4 + x-4 = 1154

Formula used:

(a + b)2 = a2 + b2 + 2ab 

Calculation:

x4 + x-4 = 1154

      or 

x4 + 1/x4 = 1154        (1) 

By adding 2 on both sides in equation (1)

⇒ x4 + 1/x4 + 2 = 1154 + 2  

⇒ (x2 + 1/x2)2 = 1156

⇒ (x2 + 1/x2) = √1156 = 34       (2)

By adding 2 on both sides in equation (2) 

⇒ (x2 + 1/x+ 2) = 34 + 2 

⇒ (x + 1/x)2 = 36

⇒ (x + 1/x) = √36 = 6

∴  x + x-1 = 6 

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.

Categories

...