Discussion Forum



1)

 If A is non-singular matrix and (A+l)(A-l)  =0 then A+A-1= ......


A) 2 A

B) 0

C) l

D) 3l

Answer:

Option A

Explanation:

We have, A is non -singular matrix

 $\therefore$   |A|=0

 and (A+l)(A-l)=0

$\Rightarrow$ A2-l2  =0

$\Rightarrow$     A2= l2 =l

 $\Rightarrow$     A.A=l $\Rightarrow$  A-1 = A

 $\therefore$ A+A-1 = A+A=2A