Решение
1,4 - 4*(2х + 1) > 1,8 -3x
1,4 - 8x - 4 > 1,8 - 3x
- 8x + 3x> 1,8 + 4 - 1,4
- 5x>4,4
x < - 0,88
1/9 а^2 -2ас+9с^2
4а^2 -12ав +9в^2
16у^4 +8ху^2 +х^2
ОДЗ x^2-3<span>≠0</span>
x^2<span>≠3</span>
<span>x<span>≠корень 3</span></span>
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<span><span>ОДЗ</span></span>
x^2+6x-7<span>≠0</span>
<span>x1<span>≠1; x2<span>≠-7</span></span></span>
D=b^2-4ac=441-4*5*22=441-440=1
x1=(21-1)/10=2
x2=(21+1)/2=2,2
ответ:2 и 2,2
Cosπ/7*cos4π/7*(-cos2π/7)=(-sinπ/7*cosπ/7*cos2π/7*cos4π/7)/sinπ/7=
=(-sin2π/7*cosπ/7*cos2π/7*cos4π/7)/2sinπ/7=(-sin4π/7*cos4π/7)/4sinπ/7=
=(-sin8π/7)/8sinπ/7=(-sinπ/7)/8sinπ/7=-1/8