Q=b2:b1=-250/(-1250)=1/5
b1•(q^5–1) -1250•(1/3125–1)
S5 = --------------- = ----------------------- =
q–1 -4/5
-7/5
= ------- = (7•5)/(5•4) = 7/4
-4/5
<em>18=2х+28
-2х=18-18
2х=-18+18
2х=0
х=0</em>
(a+0,5b)^2-(0,5a+b)^2=a^2+ab+0.25b^2-(0.25a^2+ab+b^2)=0.75a^2+ab+0.25b^2-ab-b^2=0.75a^2+0.25b^2-b^2=0.75a^2-0.75b^2
0.75*3^2-0.75*(-2)^2=0.75*9-0.75*(-2)^2=6.75-0.75*4=6.75-3=3.75