Bài 1:

a: =>(x-3)(x-1)>0

=>x>3 hoặc x<1

b: =>(x+3)(x-2)>0

=>x>2 hoặc x<-3

c: =>(x-1)(5x-3)<=0

=>3/5<=x<=1

Bài 2: 

a: =>x+2/2x-5>0

=>x>5/2 hoặc x<-2

b: =>x-5/x+3<=0

=>-3<x<=5

bài gì

đề bài đâu r

a) \(A=\dfrac{1}{1.3}+\dfrac{1}{3.5}+\dfrac{1}{5.7}+...+\dfrac{1}{19.21}\)

\(A=\dfrac{1}{2}.\left(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{19}-\dfrac{1}{21}\right)\)

\(A=\dfrac{1}{2}.\left(1-\dfrac{1}{21}\right)\)

\(A=\dfrac{1}{2}.\left(\dfrac{21}{21}-\dfrac{1}{21}\right)\)

\(A=\dfrac{1}{2}.\dfrac{20}{21}\)

\(A=\dfrac{10}{21}\)

b) \(B=\dfrac{1}{99}-\dfrac{1}{99.98}-\dfrac{1}{98.97}-\dfrac{1}{97.96}-...-\dfrac{1}{3.2}-\dfrac{1}{2.1}\)

\(B=\dfrac{1}{99}-\left(\dfrac{1}{1.2}+\dfrac{1}{2.3}+...+\dfrac{1}{96.97}+\dfrac{1}{97.98}+\dfrac{1}{98.99}\right)\)

\(B=\dfrac{1}{99}-\left(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+...+\dfrac{1}{96}-\dfrac{1}{97}+\dfrac{1}{97}-\dfrac{1}{98}+\dfrac{1}{98}-\dfrac{1}{99}\right)\)

\(B=\dfrac{1}{99}-\left(1-\dfrac{1}{99}\right)\)

\(B=\dfrac{1}{99}-\left(\dfrac{99}{99}-\dfrac{1}{99}\right)\)

\(B=\dfrac{1}{99}-\dfrac{98}{99}\)

\(B=-\dfrac{97}{99}\)