Х=0 у=2*0-1=-1
х=1 у=1*2-1=1
х=2 у=2*2-1=3
3a-8a²b=a(3-8ab)....................
1)
b1 = 27; b2 = 24
bn = b1+(n-1)d
bn = bn-1+d
d = b2-b1 = -3
b21 = 27-3*20 = -47
2)
c2 = -9; c3 = -5
d = c3-c2 = 4
c1 = c2-d = -13
Sn = n(2c1+d(n-1))/2
S8 = (-26+4(8-1))*8/2 = 8
ODЗ: 2х-1>0 2x>1 x>1/2
Log7 (2x-1)<Log7 7²
2x-1<49 2x<50 x<25
-////////////////1/2////\\\\\\\\\\\\\\\\\\\\\\\\\\////////////\\\25\\\\\\\
точки 1/2 и 25 не входят в решение неравенства х∈(1/2;25)