1.а)b5=3*(0,5)^4=3/16
б)q=1/5 b5=5*(1/5)4=5*1/625=1/125
2)a)b1=5/2 b2=1 q=1:5/2=2/5
S5=5/2(1-32/3125):(1-2/5)=5/2*3093/3125*5/3=1031/250=4 31/250
б)q³=108/4=27 q=3 b1=4/9
S5=4/9(81-1):(3-1)=4/9*80:2=160/9= 17 7/9
3a 6a a
(------------ - -------------------- ) : ----------- =
4 - a a² + 16 - 8a 4 - a
3a 6a 4 - a
= (------------ - -------------- ) * ----------- =
4 - a (4 - a)² a
3a * (4 - a) - 6a 4 - a
= --------------------------- * ----------- =
(4 - a)² a
3 * (4 - a) - 6 12 - 3a - 6 6 - 3a
= ----------------------- = -------------------- = ------------
4 - a 4 - a 4 - a