А)67*0,2=13,4, б)-75,7*10=-757, в)-(25*15,8*4),-(395*4)=1580,г)0,47*10=4,7.
D=b(квадрат)-4ас;
D=(-10)(квадрат)-4*(-2)*(-8);
D=36=6(квадрат);
x1=-b-кореньD/2a;
x2=-b+кореньD/2a;
x1=10-6/-4=-1
х2=10+6/-4=-4
A)sin2*75=sin150=1/2
b)sin π/4 = √2/2
c) 1/2 sin30 = 1/2 * 1/2=1/4
d)cos² π/8+sin² π/8 +2sin π/8cosπ/8 = 1+sinπ/4 = 1+ √2/2
e)sin² π/12 +cos²π/12 -2sin π/12cos<span>π/12= 1-sin </span>π/6 = 1-1/2=1/2
f)cos2*75 = cos 150=1/2
g)cos π/4 = √2/2
h)1-cos² π/12 - cos² π/12 = sin² π/12 - cos ² π/12 = -cos π/6= -√3/2
Ответ: получится 12 корней 3
4/10×2/7+23/10×3/7=8/70+69/70=77/70=1.1