X² > 49
x₁= -7 x₂= 7
////////////XXXXX
---------₀---------₀------->x
-7 7
x>7
x∈(7; +∞)
(sinα+cosα)²=2-(sinα-cosα)
1. (sinα+cosα)²=sin²α+2sinα*cosα+cos²α=
=(sin²α+cos²α)+2sinα*cosα=1+2sinα*cosα
2. 2-(sinα-cosα)²=2-(sin²α-2sinα*cosα+cos²α)=2-(sin²α+cos²α-2sinα*cosα)=
=2-(1-2sinα*cosα)=2-1-(-2sinα*cosα)=1+2sinα*cosα
3. 1+2sinα*cosα=1+2sinα*cosα
ч. т. д.
(x^8 y^3)/(x^2 y^7) = (х^6)/(y^4)