А14=a1+13d=140
s14=1/2(a1+a14)*14=1/2(2a1+13d)*14=1050
a1=140-13d 7(280-26d+13d)=7(280-13d)=1050 280-13d=150
13d=280-150=130 d=10
a1=140-130=10
12а²-18а-а²-4а-а-4=11а²-13а-4
Преобразуем левую часть 2sin^2(45-1t)+sin(4t)=
<span>1-cos(90-4t)+sin(4t)=1-sin(4t)+sin(4t)=1</span>
Tgx= -1
tgx = -π/4 +πk
tgx=0
x=πk