15^x=a1/(a+31)-4/(5a-1)≤0(5a-1-4a-124)/(a+31)(5a-1)≤0(a-125)/(a+31)(5a-1)≤0a=125 a=-31 a=1/5 _ + _ +-------------(-31)----(1/5)---------[125]-----------a<-31⇒5^x<-31 нет решения1/5<a≤125⇒1/5<5^x≤125⇒-1<x≤3x∈(-1;3]21)4^x-29*26x+168≤02%x=aa²-29a+168≤0a1+a2=29 U a1*a2=168⇒a1=8 U a2=218≤a≤21⇒8≤2^x≤21⇒3≤x≤log(2)212)x²+(3x-25)/x(x-5)≥x²-1/(x-4)+5/x(3x-25)+1/(x-4)-5/x≥0(3x²-12x-25x+100+x²-5x-5x²+45x-100)/x(x-4)(x-5)≥0(-x²+3x)/x(x-4)(x-5)≥0x(x-3)/x(x-4)(x-5)≤0(x-3)/(x-4)(x-5)≤0x=3 x-4 x=5 x≠0 _ + _ +---------[3]--------(4)----------(5)-----------x∈(-∞;0) U (0;3] U (4;5)