ctg(x/3 + 2π/3) > -1;
πn < x/3 + 2π/3 < 3π/4 + πn, n∈Z;
-2π/3 + πn < x/3 < π/12 + πn, n∈Z;
-2π + 3πn < x < π/4 + 3πn, n∈Z;
Ответ: х∈(-2π + 3πn; π/4 + 3πn), n∈Z
A8 = a1 + 5d + 2d = a6 + 2d = 6
a6 = 6 - 2d = 6 - 2(-1) = 6 + 2 = 8
4,6x(0,2x-0,3y) = 0.92x²-1.38xy
(2x-3y)(4x+5y) = 8x²+10xy-12xy-15y² = 8x²-2xy+15y²
<span>(3x-4y)^2 = 9x</span>²-24xy+16y²
=(3x*3b+5x*6a-7*2b)/12a²b²=(9bx+30ax-14b)/12а²b²
X(x-7)=0
x=0
x-7=0
x=7
<span>Ответ: x=0; x = 7</span>