1) (3x+4x)/(9-x)amp;gt;0 2) log0.25 (3x-5)amp;gt;-3 3) 2cos(x/2)+1=0

1) (3x + 4x)/(9 - x) gt; 0;

x(3x + 4)/(9 - x) gt; 0;

-3x(x + 4/3)/(x - 9) gt; 0;

x(x + 4/3)/(x-9) lt; 0;

x  (-; -4/3)  (0; 9).

2) log, (3x - 5) gt; -3;

log, (3x - 5) gt; log, 0,25;

3x - 5 lt; 0,25 = 4 = 64;

3x lt; 64 + 5 = 69;

x lt; 69 / 3 = 23;

x lt; 23.

3) 2cos(x/2) + 1 = 0;

2cos(x/2) = -1;

cos(x/2) = -1/2;

x/2 = arccos(-1/2) + 2n, n целое;

x = 2arccos(-1/2) + 4n, n целое.