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Suppose that|a - b| + |b - c| + |c - a| = 20.What is the maximum possible value of |a - b|?

 Jan 10, 2015

Best Answer 

 #1
avatar+128475 
+5

Abs (a - b) will be largest when at least one of the other terms is minimized....so, since absolute value is always ≥ 0, let's minimize the middle term by letting b = c

This gives us

abs ( a - b)   + abs(c - a)  = 20   but, since  b= c, we can write

abs ( a - b)   + abs(b - a)  = 20  and let's assume  that a > b  [we could also assume the opposite....it won't matter]

So we have, using the definition of absolute value:

a - b  + -(b - a)  = 20

a - b  + a - b = 20

2(a - b)  = 20

(a - b)  = 10

Which implies that

abs (a - b) = 10

And that's as large as  abs(a - b) can be

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As Melody would say.......that's what I think..!!!.....of course....any constructive criticism is welcome....!!!

 

 Jan 11, 2015
 #1
avatar+128475 
+5
Best Answer

Abs (a - b) will be largest when at least one of the other terms is minimized....so, since absolute value is always ≥ 0, let's minimize the middle term by letting b = c

This gives us

abs ( a - b)   + abs(c - a)  = 20   but, since  b= c, we can write

abs ( a - b)   + abs(b - a)  = 20  and let's assume  that a > b  [we could also assume the opposite....it won't matter]

So we have, using the definition of absolute value:

a - b  + -(b - a)  = 20

a - b  + a - b = 20

2(a - b)  = 20

(a - b)  = 10

Which implies that

abs (a - b) = 10

And that's as large as  abs(a - b) can be

--------------------------------------------------------------------------------------------------------------------------

As Melody would say.......that's what I think..!!!.....of course....any constructive criticism is welcome....!!!

 

CPhill Jan 11, 2015

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