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Question: Answered & Verified by Expert
If A is a symmetric matrix and B is skew- symmetric matrix such that  A+B=235-1 , then AB is equal to:
MathematicsMatricesJEE MainJEE Main 2019 (12 Apr Shift 1)
Options:
  • A -4214 
  • B 4-21-4
  • C 4-2-1-4
  • D -4-2-14
Solution:
2228 Upvotes Verified Answer
The correct answer is: 4-2-1-4
Given A is symmetric and B is skew symmetric, hence 
A=abbc and B=0d-d0
Now A+B=ab+db-dc=235-1
a=2,  b=4,  c=-1 and d=-1
A=244-1 and B=0-110
Hence AB=244-10-110=4-2-1-4

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