-1 <= cos 2x <= 1
-4 <= 4cos2x <= 4
<span>-7 <= -3+4cos2x <= 1</span>
<span></span>
<span>y ∈ [-7; 1]</span>
-1<=сos2x<=1
-4<=4cos2x<=4
-7<=-3+4cos2x<=1
[-7;1]
на фото................