(a+1)²+(а-1)² а²+2а+1 + а²-2а+1
------------------ = --------------------------- =
3а²+3 3(а²+1)
2(а²+1)
------------- = 2/3
3(а²+1)
.....................................................................................
2)4x-3≥0 ⇒ x≥3/4
(3x-4)√(4x-3)≤0
x≤4/3 x≤3/4
otvet:x=3/4;x∈[3/4;4/3]
3)16x-x³/ √(x²-16)≥0
a)16x-x³≥0⇒x≥0;x≤4;x≤-4
a)√(x²-16)>0⇒x>4;x>-4
b)16x-x³≤0⇒x≤0;x≥4;x≥-4
b)√(x²-16)<0⇒x<4;x<-4
otvet x=4; x∈[0;4);x∈(-4;0]
1)2x-5>0
x>5/2
√(4x²+7) +3≥0
4x²+7≥9
x²≥2/4⇒x≥√2/2;x≥-√2/2
otvet:x∈(-∞;-√2/2] ∨ [√2/2;+∞); x=5/2
Условие можно прочитать двумя способами :
Cos126° = Cos(90° + 36°) = - Sin36°
Или так:
Cos126° = Cos(180° - 54°) = - Cos54°
Cos234° = Cos (270° - 36°) = - Sin36°
Cos234° = Cos(180° + 54°) = - Cos54°
Cos306° = Cos(270° + 36°) = Sin36°
Cos306° = Cos(360° - 54°) = Cos54°