1
2^x=a
a²-29a+168≤0
a1+a2=29 U a1*a2=168⇒a1=8 u a2=21
8≤a≤21⇒8≤2^x≤21⇒3≤x≤log(2)21
x∈[3;log(2)21]
2
5^2x-5*5^x*2^x-6*2^2x≤0/2^2x
(5/2)^2x-5*(5/2)^x-6≤0
(5/2)^x=a
a²-5a-6≤0
a1+a2=5Ua1*a2=-6⇒a1=-1 U a2=6
-1≤a≤6⇒-1≤(2,5)^x≤6⇒x≤log(2,5)6
x∈(-∞;log(2,5)6]
3
2^x=a
(7-2a)/(a²-12a+32)≥1/4
(28-8a-a²+12a-32)/(a²-12a+32)≥0
(a²-4a+4)/(a²-12a+32)≤0
(a-2)²/(a-4)(a-8)≤0
a=2 a=4 a=8
+ + _ +
------------[2]---------(4)------------(8)----------------------
44<2^x<8 U 2^x=2<br>2x∈(2;3) U {1}