Solve the following equation?

#(2x)/(2x^2+5x+2)>1/(x+1)#

1 Answer
Jun 16, 2018

#-2/3 < x < -1/2# and #-2 < x <-1# only

Explanation:

#(2x)/(2x^2+5x+2) > 1/(x+1)# where #x!=-1,-1/2,-2#

#(2x)/(2x^2+5x+2) -1/(x+1) >0#

#(2x(x+1)-(2x^2+5x+2))/((x+1)(2x^2+5x+2)) >0#

#(2x^2+2x-2x^2-5x-2)/((x+1)(2x^2+5x+2)) >0#

#(-3x-2)/((x+1)(2x^2+5x+2)) >0#

#((x+1)(2x^2+5x+2))^2times(-3x-2)/((x+1)(2x^2+5x+2)) >0times((x+1)(2x^2+5x+2))^2#

#color (red) ("you need to multiply both sides by the denominator squared because you don't know whether your denominator is a positive or negative number. If it was negative, then your inequality sign would change."#

#(-3x-2)(x+1)(2x^2+5x+2) >0#

#(-3x-2)(x+1)(2x+1)(x+2)>0#

#-(3x+2)(x+1)(2x+1)(x+2)>0#

graph{(-3x-2)(x+1)(2x+1)(x+2) [-10, 10, -5, 5]}

looking at the graph, we can see that
#-2/3 < x < -1/2# and #-2 < x <-1# only