Question

Solve (2x-1)(x+1)<0

Answer 1

2x-1<0
2x<1
x<1/2

x+1<0
x<-1

Therefore the solution is x<1/2

Answer 2

but you found a second solution of x<-1

Answer 3

x<-1 is also<1/2, Therefore all solutions are <1/2