Tip:A–D to answerE for explanationV for videoS to reveal answer
Let A,B be n×n matrices such that BA+B2=I−BA2, where I is the n×n identity matrix. Which of the following is always true?
- A.
A is non-singular
- B.
B is non-singular
(Correct Answer) - C.
A+B is non-singular
- D.
AB is non-singular
Correct Answer: B is non-singular
Explanation
Solving:
-
Equation: BA+B2+BA2=I
-
Taking B common from left: B(A+B+A2)=I
-
Condition for Non-Singular:
If X⋅Y=I, then ∣X∣⋅∣Y∣=∣I∣=1
⟹∣B∣=0 and ∣A+B+A2∣=0
Since ∣B∣=0, B is hamesha non-singular hoga.
Sahi Option: (b) B is non-singular
Explanation
Solving:
-
Equation: BA+B2+BA2=I
-
Taking B common from left: B(A+B+A2)=I
-
Condition for Non-Singular:
If X⋅Y=I, then ∣X∣⋅∣Y∣=∣I∣=1
⟹∣B∣=0 and ∣A+B+A2∣=0
Since ∣B∣=0, B is hamesha non-singular hoga.
Sahi Option: (b) B is non-singular