#(2-3x)(x^3+4)<=0#
Use the distributive property. #(2)(x^3)+(2)(4)+(-3x)(x^3)+(-3x)(4) <=0# #2x^3 + 8 - 3x^4 - 12x <=0# #-3x^4 +2x^3 - 12x + 8 <=0#
Let's find the critical points of the inequality. #-3x^4 +2x^3 -12x+8 =0#
Factorize the left side #(-3x+2)(x^3+4)=0#
Set factors equal to 0 #-3x + 2=0 or x^3 +4=0# #x=2/3 or x=-1.587401#