An Absolute-Value Inequality

Problem

Prove that for all reals a,b,ca, b, c,

∣a∣+∣b∣+∣c∣+∣a+b+c∣≥∣a+b∣+∣b+c∣+∣c+a∣,|a| + |b| + |c| + |a+b+c| \ge |a+b| + |b+c| + |c+a|,

and determine exactly when equality holds.

Answer

Solution

Difficulty7/10
TopicsAbsolute Value, algebra, inequality, Casework

Whiteboard

Your sketch is saved only in this browser. To share it, export your drawing as an image (whiteboard menu → Export as → PNG), then upload that image in the comments below.

Discussion

Ask questions, share alternate solutions, and use LaTeX freely.

0 comments
Log in to join the discussion.

No comments yet.