Expert: Bobby Soltani - 11/5/2004

Question
Trying to help my kid with a math problem:

40-[x]<[40-x]

x=?

Answer
Hi Len,

The answer is x<0 and x>40.  The best way to figure this one out is to graph it.  It is hard for me to show you how to graph it with only this text.  Let the first equation be the left hand side and the second equation be the right hand side.

1. y = 40-abs(x)
y = 0 at x = 40 and x = -40.  y=40 at x = 0.  Connect these three points and extend them outward.

2. y = abs(40-x)
y = 0 at x = 40.  y = 40 at x = 0. y = 40 at x = 80.  Extend these outward from x=40 upward in both directions.  Now the x intervals where 1 < 2 is the answer.

I know this is a confusing explanation.  For each of the graphs, draw a line from the middle point through the outer points listed.

I hope this helps you.  Please let me know if you hand futher questions and I will be glad to clarify anything.

Bobby