a,$\frac{2x+5}{4}$ <$\frac{3x-2}{5}$
⇔8x+25<12x-8
⇔8x-12x<-25-8
⇔-4x<-33
⇔x<$\frac{25}{4}$ hay x < 8,25
vậy S={x|x<$\frac{25}{4}$
b,(x+2)²< 4x+6
⇔x²+4x+4<4x+6
⇔x²<2
⇔x<√2
vậy S={x|x<√2}
c,4x+9>9
⇔4x>0
⇔x>0
vậy S={x|x>0}
d,$\frac{x-2}{3}$ ≥x-$\frac{x-1}{2}$
⇔2x-6≥6x-3x+3
⇔-x≥9
⇔x≤-9
vậy S={x|x≤-9}