August 7th, 2019, 11:14 PM  #1 
Newbie Joined: Jul 2019 From: jakarta Posts: 3 Thanks: 2  weird mistake?
Guys, I need help in reasoning this: (7x+12)/x > 3 7x+12 > 3x 4x > 12 x > 3 but if you sketch the graph it's obvious that my answer is wrong. What is wrong with the steps? Last edited by skipjack; August 7th, 2019 at 11:37 PM. 
August 7th, 2019, 11:41 PM  #2 
Senior Member Joined: Sep 2015 From: USA Posts: 2,529 Thanks: 1389 
Be careful when dividing by variables. When they are negative the inequality flips direction. 
August 7th, 2019, 11:50 PM  #3 
Global Moderator Joined: Dec 2006 Posts: 20,921 Thanks: 2203 
The first step "reverses" the inequality if x < 0. Multiplying by x² instead leads to the correct solution: x < 3 or x > 0. 
August 14th, 2019, 12:37 AM  #4 
Newbie Joined: Jul 2019 From: jakarta Posts: 3 Thanks: 2  

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