X>0
<span>¼log₂x+½log₂x+log₂x=7 (•4) </span>
<span>log₂x+2log₂x+4log₂x=28 </span>
<span>7log₂x=28 </span>
<span>log₂x=4 </span>
x = 16
не уверена.
2cos 2x + sin^2 x = 2(1 - 2 sin^2x) + sin^2 x =2 - 4 sin^2 x + sin^2 x =
=2 - 3 sin^2 x = 2 - 3 * (1/3)^2 = 2 - 3 * 1/9 = 2 - 1/3 = 5/3