20х^3 - 8х^2 +4 при х= -0,1
20 * (-0,1)^3 - 8 *(-0,1)^2 + 4 = 20 *(-0,001) - 8 * 0,01 + 4 = -0,02 - 0,08 + 4 = -0,1 +4= 3,9
X^2+6xy+9y^2-1=(x+3y)^2-1=(x+3y-1)(x+3y+1)
1)-3х-6=5-2х;
-3х+2х=5+6;
-х=11;
х=-11;
2)3-5х-5=6-4х;
-5х+4х=5-3;
-х=2;
х=-2;
Ответ:1)-11; 2)-2.
2cos²6x ≤1,5;
cos²6x ≤3/4;
|cos6x| ≤1/2*√3
- 1/2*√3≤ cos6x ≤1/2*√3 .
a) π/6 ≤ 6x ≤ π -π/6 ;
π/6 ≤6x ≤5π/6 ;
2π*k +π/6 ≤6x ≤5π/6+ 2π*k ;
π/3*k +π/36 ≤ x≤ 5π/36 +π/3*k , k∈Z
b) π+π/6 ≤ 6x ≤ 2π -π/6 ;'
7π/6 ≤ 6x ≤ 11π/6 ;
2π*k + 7π/6 ≤ 6x ≤ 11π/6 + 2π*k ;
π/3*k + 7π/36 ≤ x ≤ 11π/36 + π/3*k ;
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x ∈[ π/3*k +π/36 ; 5π/36 +π/3*k ] U [π/3*k + 7π/36 ;11π/36 + π/3*k ] k∈Z