99,999^2 - 1^2 =
A. 10^10 - 2
B. (10^5 - 2)^2
C. 10^4(10^5 - 2)
D 10^5(10^4 - 2)
E. 10^5(10^5 - 2)
A. 10^10 - 2
B. (10^5 - 2)^2
C. 10^4(10^5 - 2)
D 10^5(10^4 - 2)
E. 10^5(10^5 - 2)
99,999^2 - 1^2. This is of form a^2 - b^2
= [a+b]*[a-b]
= [99,999+1]*[99999-1]
= [100,000]*[100000-2]
= 10^5[10^5-2]
IMO E
