Greatest prime factor?

[kevind147]

What is the greatest prime factor of 4^17-2^28?

a. 2
b. 3
c. 5
d. 7
e. 11

The answer is e ... how?

[scoobydooby]

i get 7

4^17-2^28
=>(2^2)^17-2^28
=>2^34-2^28
=>2^28(2^6-1)
=>2^28(64-1)
=>2^28*63
=>(2^28)*(3^2)*7 (broken down in the prime factors)

=>7 greatest prime

[tdadic84]

i also get 7...please confirm ur answer

[bjp2008]

i also get 7...please confirm ur answer

I also get 7.

[kevind147]

i also get 7...please confirm ur answer

I also get 7.

• my bad, it is 7. sorry everyone.