4²+2³-0,7*4=16+8-2,8=21,2
Правильный ответ:А)21,2
1. Подставим n=1 и n=2
a1=3*1+2=5
a2=3*2+2=8
d=n2-n1=8-5=3
Sk=(2a1+(k-1)*d)*k/2
S5=(2*5+4*3)*5/2=55
S40=(2*5+39*3)*40/2=317
2/ An=a1+d(n-1)
A7=a1+6d
24=8+6d⇒ d=16/6=8/3
S10=(2a1+9d)*10/2=(16+24)*5=200
(м х4)-73=183
м х 4=183+73
м х 4=256
м=256:4
м=64
(42-у) х 3=96
42-у=96:3
42-у=32
у=42-32
у=10
х+х+21=165
2х=165-21
2х=144
х=144:2
х=72-первое число
72+21=93-второе число
(cos23π/12-sin11π/12)(sin17π/12-cos19π/12)
=(cos(2π-π/12)-sin(π-π/12))*
(sin(π+5π/12)-cos(2π-5π/12)=
(cosπ/12-sinπ/12)(-sin5π/12-cos5π/12)=
(cosπ/12-sinπ/12)(-sin(π/2-π/12)-
cos(π/2-π/12))==
(cosπ/12-sinπ/12)(-1)(cosπ/12+sinπ/12)=
-(cos²π/12-sin²π/12)=-cosπ/6=-√3/2