sriramsundaram91 wrote:
I think except forBunuel all others are wrong, they simply take the 3z to the other side of the inequality without knowing whether z is positive or negative. Sorry If I am rude, but taking a variable to the other side of the inequality without knowing its sign is just plain wrong. If z were positive there is no change in the inequality sign, but if z were negative we must change the direction of the inequality. Thus the approach of adding two equations seem to be flawless.
So please don't take
...