185. а1=103, d = -2
а) S(n) = (2a1+d(n-1))*n/2. Тогда:
S(8) = (206 - 14)*8/2 = 768
б) S(103) = (206 - 204)*103/2 = 103
186.
а)А₁=7,d=4, n=13;
a(n) = a(1)+d(n-1) = 7+4n-4 = 4n+3 = 55
S(n) = (14+4(n-1))*n/2 = 403
б)А₁=2,d=2,n=40;
A(n) = 2+2*39 = 80;
S(n) = (4+2*39)*40/2 = 1640
в)A₁=56,d=-3,n=11
A(n) = 56 - 3*10 = 26
S(n) = (112-3*10)*11/2= 451
188. Y1= -32, d = 5
a) S(10) = (-64 + 5*9)*10/2 = -95
б) S(26) = (-64 + 5*25)*26/2 = 793
189. a1 = 25, d = -4,5
a) S(16) = (50-4,5*15)*16/2 = - 140
б) S(40) = (50 - 4,5*39)*40/2 = - 2510
185. а1=103, d = -2
а) S(n) = (2a1+d(n-1))*n/2. Тогда:
S(8) = (206 - 14)*8/2 = 768
б) S(103) = (206 - 204)*103/2 = 103
186.
а)А₁=7,d=4, n=13;
a(n) = a(1)+d(n-1) = 7+4n-4 = 4n+3 = 55
S(n) = (14+4(n-1))*n/2 = 403
б)А₁=2,d=2,n=40;
A(n) = 2+2*39 = 80;
S(n) = (4+2*39)*40/2 = 1640
в)A₁=56,d=-3,n=11
A(n) = 56 - 3*10 = 26
S(n) = (112-3*10)*11/2= 451
188. Y1= -32, d = 5
a) S(10) = (-64 + 5*9)*10/2 = -95
б) S(26) = (-64 + 5*25)*26/2 = 793
189. a1 = 25, d = -4,5
a) S(16) = (50-4,5*15)*16/2 = - 140
б) S(40) = (50 - 4,5*39)*40/2 = - 2510
D=1+48=49
x=(-1+7)/6=1
x=(-1-7)/6= -4/3
+ - +
-4/31
x∈(-∞;-4/3)∪(1;+∞)
б) f(x)= 2x + x^2/2 - x^3/3
f⁾(x)= 2+х-х²
D=1+8=9
x=(-1+3)/(-2)=-1
x=(-1-3)/(-2)=2
- + -
-12
x∈(-1; 2)