i) 85.(35-27)-35.(85-27)
=(85.35-85.27)-(35.85-35.27)
=85.35-85.27-35.85+35.27
=85.35-35.85-85.27+35.27
=-85.27+35.27
=(-85+35).27
=-50.27
=-1350
m) $2^{100}$ - $2^{99}$ - $2^{98}$ - ... - $2^{2}$ - 2 - 1
= $2^{100}$ - ($2^{99}$ + $2^{98}$ + ... + $2^{2}$ + 2 + 1)
Đặt : B = $2^{99}$ + $2^{98}$ + ... - $2^{2}$ + 2 + 1
Ta có: B.2 = 2($2^{99}$ + $2^{98}$ + ... - $2^{2}$ + 2 + 1)
= $2^{100}$ + $2^{99}$ + $2^{98}$ + ... + $2^{2}$ + 2
2B-B= ($2^{100}$ + $2^{99}$ + $2^{98}$ + ... + $2^{2}$ + 2)-($2^{99}$ + $2^{98}$ + ... - $2^{2}$ + 2 + 1)
B=$2^{100}$-1
Vậy $2^{100}$ - $2^{99}$ - $2^{98}$ - ... - $2^{2}$ - 2 - 1
=$2^{100}$-($2^{100}$-1)
= 1
