Solving inequalities why flip sign

Example Solve the inequality. Get access to the complete Algebra 1 course. Get started. Learn math Krista King November 30, math , learn online , online course , online math , algebra , algebra 1 , algebra i , inequalities , negative numbers , multiplying by a negative , dividing by a negative , inequality.

Learn math Krista King November 30, math, learn online, online course, online math, geometry, rectangles, perimeter, perimeter of a rectangle, rectangular perimeter, area and perimeter, length and width, two parallel sides. You also often need to flip the inequality sign when solving inequalities with absolute values.

How to Divide Negative Fractions. How to Solve Double Inequalities. Standard Form of a Linear Equation. How to Solve Inequalities With Fractions. How to Divide Negative Numbers. How to Determine Linear Equations. How to Do Math Problems in Algebra 1. How to Calculate the Equation of a Line. The solution to the set of inequalities is the overlapping graphical area. Get Link.

You cannot divide by y or 5y since you do not know whether y is negative or positive and, as such, you do not know whether to flip the inequality. Active 1 year, 2 months ago. Viewed k times. Sniper Clown Sniper Clown 1, 2 2 gold badges 17 17 silver badges 34 34 bronze badges. Instead I give link on Inequalities by Lawrence Spector which answers it in thorough detail introducing theorem of inequalities and their proofs.

Add a comment. Active Oldest Votes. Seeing why 1 is true is not too hard. The other cases can be handled similarly. But, perhaps a bit of rigor is needed here. David Mitra David Mitra Either it is circular or so incomplete to be of little help. Alas, the OP doesn't know what he's missing by accepting it. Perhaps you may wish to do him a favor by improving the answer. However, after reading your answer it appears the short and straight answer is because of law of signs which I think is what I was looking for.

The reason that the reversal for equality escapes notice is that the symbol for equality is symmetric.