1)x(3x+4)/(9-x)>0

+++(-4/3)---(0)+++(9)----

x=(-∞;-4/3)U(0;9)

2)одз 7x-4>0; x>4/7

log(2)(7x-4)=log(2)4+log(2)13

log(2)(7x-4)=log(2)52

7x-4=52; 7x=48; x=48/7

3)sin^2x+cos^2x=1

sin^2x=1-cos^2x=1-(8/17)^2=225/289

sinx=15/17