Question

correct answer is c how ?​

Answer 1

For A²=A -> A=I

I³=I²=I

-> (I+A)³=(I+I)³=(2I)³=8I³=8I=8A

->(I+A)³ -7A=8A -7A=A.

Hope it helps...

Regards;

Leukonov/Olegion.