Question 660689
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Hi, there--

You could start by dividing your proof into three cases:
a is negative (i.e. a<0).
a is positive (i.e a>0).
a is zero (i.e. a=0). This is the easy one (o:

Show what the absolute value function does to a in each case. Start there and see how far you 
get. You may email me directly if you have more questions, or repost here.

Then again, another tutor might post the whole proof for you (o:

Mrs. Figgy
math.in.the.vortex@gmail.com
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