请各位帮我解下 "|4x-1|大于等于9" 这个不等式~~~

(1).当4x-1≥0时,即x≥1/4
|4x-1|≥9去掉绝对值,得4x-1≥9,得x≥5/2
取x≥1/4和x≥5/2的交集得解集x≥5/2
(2).当4x-1<0时,即x<1/4
|4x-1|≥9去掉绝对值,得-(4x-1)≥9,得x≤-2
取x<1/4和得x≤-2的交集得解集x≤-2

取(1),(2)的并集得该不等式的解集x≥5/2或x≤-2

X小于等于-2或X大于等于5/2

原不等式等价于
4x-1>(=)9或4x-1<(=)-9
x>(=)2/5或x<(=)-2

|4x-1|>9
=>9<4x-1或者4x-1<-9
=>x>2.5或者x<-2

当4X-1>9时 X>2.5
当4X-1<-9时 X<-2

9≤4x-1≤-9
10≤4x≤-8
2.5≤x≤-2