Giải thích:
-> Chứng minh S $\vdots$ 2:
S = 2 + 2² + 2³ + 2⁴ +.......+ 2⁹⁹ + 2¹⁰⁰.
S = 1×2 + 2×2 + 2×2² + 2×2³ +.........+ 2×2⁹⁸ + 2×2⁹⁹.
S = 2( 1+ 2 + 2² + 2³ +.........+ 2⁹⁸ + 2⁹⁹ ) $\vdots$ 2
-> S $\vdots$ 2
-> Chứng minh S $\vdots$ 5:
S = 2 + 2² + 2³ + 2⁴ +..........+ 2⁹⁹ + 2¹⁰⁰.
S = ( 2 + 2³ ) + ( 2² + 2⁴ ) +.........+ ( 2⁹⁷ + 2⁹⁹ ) + ( 2⁹⁸ + 2¹⁰⁰ )
S = 2( 1 + 4 ) + 2²( 1 + 4 ) +...........+ 2⁹⁷( 1 + 4 ) + 2⁹⁸( 1 + 4 ).
S = 2 × 5 + 2² × 5 + 2³ × 5 +.............+ 2⁹⁷ × 5 + 2⁹⁸ × 5.
S = 5( 2 + 2² + 2³ +.............+ 2⁹⁷ + 2⁹⁸ ) $\vdots$ 5
-> S $\vdots$ 5