Ta có:
4n+3 +4n+2 -4n+1 -4n
=4n-1 .44 + 4n-1 . 43 - 4n-1 . 42 - 4n-1 .4
=4n-1 . (44 +43 - 42 -4)
=4n-1 . 300 : 300
= 4n+3 + 4n+2 -4n+1 -4n \(⋮\) 300 (ĐPCM)
Đặt A=4^{n+3}+4^{n+2}-4^{n+1}-4^n
A= 4^n-1(4^4+4^3-4^2-4)
A=4^n-1.300⋮300
k cho mik nha học tốt.