Exponential Problem

[d0nw0ng]

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)

[arocks]

99,999^2 - 1^2 =?

we know that 99,999 = 10^5-1

So, (10^5 - 1)^2 - 1^2

Using, a^2-b^2=(a-b)(a+b)

(10^5-1-1) (10^5-1+1)
(10^5-2)(10^5)

So the answer is E.