a)
`-x+3\ne0`
`⇔3\ne x`
b)
`-2x-4>0`
`⇔-2x>4`
`⇔x> -2 `
c)
+)
`-2x-4>0`
`⇔x> -2` (câu b)
+)
`4+x≥0`
`⇔x≥4`
Vậy `x≥4 `
f)
+)
`2x-1\ne0`
`⇔2x\ne1`
`⇔x\ne1/2`
+)
`3x-2≥0`
`⇔3x≥2`
`⇔x≥2/3 `
Vậy `x≥2/3`
g)
+)
` 3x-5≥0`
`⇔3x≥5`
`⇔x≥5/3`
+)
`2/(x-4) > 0`
`⇔x-4>0`
`⇔x>4`
Vậy `x>4`
l)
+)
`(2x^2)/(9-4x)>0`
`⇔9-4x>0`
`⇔9>4x`
`⇔x<9/4`
+)
`x+1≥0`
`⇔x≥-1`
Vậy `-1≤x<9/4`
m)
`-5/(2x+5)>0`
`⇔2x+5<0`
`⇔2x<-5`
`⇔x<-5/2`
e)
+)
`-3x+8\ne0`
`⇔8\ne 3x`
`⇔x\ne8/3 `
+)
`(4-2x)/(8-3x)≥0`
`⇔`\(\left[ \begin{array}{l}\left \{ {{4-2x\ge0} \atop {8-3x\ge0}} \right.\\\left \{ {{4-2x\le0} \atop {8-3x\le0}} \right.\end{array} \right.\)
`⇔`\(\left[ \begin{array}{l}\left \{ {{x\le2} \atop {x\le\frac{8}{3}}} \right.\\\left \{ {{x\ge2} \atop {x\ge\frac{8}{3}}} \right.\end{array} \right.\)
Vậy `x≤2` hoặc `x>8/3`
