aₙ₊₁ = 2aₙ - 1
a₁=3
a₂ = 2*3 - 1 = 5
a₃ = 2*5 - 1 = 9
a₄ = 2*9 - 1 = 17
<span>>25 и b> 4 , то ab > 25*4 => ab>100</span>