<span>log0,5 в степ.2 (x+1)-log0,5(x+1)-2 меньше\равно 0
2(х+1)log0.5-log0.5(х+1)-2=log0.5(2(х+1)-(х+1))-2=log0.5х(х+1)-2=log1/2х(х+1)-2=-log2(х+1)=меньше/равно 0
-(х+1) меньше/равно 0
х+1 больше/равно 0
х больше - 1</span>
6.
sin51°cos39°-sin21°cos9°=sin(90°-39°)cos39°-sin21°cos9<span>°=
=cos39</span>°cos39°-sin(30°-9°)cos9°=cos²39°-sin(30°-9°)cos9<span>°=
=(cos(30</span>°+9°))² - (sin30°cos9°-cos30°sin9°)cos9<span>°=
=(cos30</span>°cos9°-sin30°sin9°)² - (¹/₂ cos9° - (√3/2) sin9°)cos9<span>°=
=((</span>√3/2) cos9° - ¹/₂ sin9°)² - ¹/₂ cos² 9° + (√3/2) sin9° cos9<span>° =
= </span>³/₄ cos² 9° - (√3/2)sin9° cos9° + ¹/₄ sin² 9° - ¹/₂ cos² 9° + +(√3/2)sin9°cos9<span>°=
= </span>³/₄ cos² 9° - ²/₄ cos² 9° + ¹/₄ sin² 9<span>° =
= </span>¹/₄ cos² 9° + ¹/₄ sin² 9<span>° =
= </span>¹/₄ (cos² 9° + sin² 9<span>°</span>)= ¹/₄ * 1 = ¹/₄
<span>x²-7x+12=0
D = (-7)</span>² - 4 * 1 * 12 = 49 - 48 = 1
-(-7) + 1
x₁ = ---------------- = 8/2 = 4
2*1
-(-7) - 1
x₂ = ------------------- = 6/2 = 3
2 * 1
x₁ - x₂ = 4 - 3 = 1
y= - 4x - 6 y = - 2x - 4
- 4x - 6 = - 2x - 4
- 4x + 2x = 6 - 4
- 2x = 2
x = - 1
y = - 2 * (- 1) - 4 = 2 - 4 = - 2
Координаты точки пересечения : ( - 1 ; - 2)