SOLUTION: A student is asked to solve b^2+b^2=c^2 for a and gives the following solution. Assume all variables represent positive Real Numbers. (Step 1) {{{ b^2+a^2=c^2 }}} (Step

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: A student is asked to solve b^2+b^2=c^2 for a and gives the following solution. Assume all variables represent positive Real Numbers. (Step 1) {{{ b^2+a^2=c^2 }}} (Step       Log On


   



Question 964233: A student is asked to solve b^2+b^2=c^2 for a and gives the following solution. Assume all variables represent positive Real Numbers.
(Step 1) +b%5E2%2Ba%5E2=c%5E2+
(Step 2) +sqrt%28+b%5E2%2Ba%5E2+%29+=+sqrt%28+c%5E2+%29+
(Step 3) b+a=c
(Step 4) a=c-b

Explain the mistake(s) made by the student and provide the correct solution. Make sure to analyze the entire solution as there may be multiple mistakes made.
I cannot figure out the answers to this question. I think I might have the answers but I am not sure they are correct. Any help would be appreciated!

Found 2 solutions by Alan3354, Edwin McCravy:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
(Step 1) +b%5E2%2Ba%5E2=c%5E2+
(Step 2) +sqrt%28+b%5E2%2Ba%5E2+%29+=+sqrt%28+c%5E2+%29+
(Step 3) b+a=c
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Step 3 is not correct.
(b + a)^2 <> b^2 + a^2

Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!
A student is asked to solve b^2+a^2=c^2 for a and gives the following
solution. Assume all variables represent positive Real Numbers. 

(Step 1)       +b%5E2%2Ba%5E2=c%5E2+
(Step 2)       +sqrt%28+b%5E2%2Ba%5E2+%29+=+sqrt%28+c%5E2+%29+
(Step 3)       b+a=c

That step is wrong. This mistake is trying to use a rule that applies 
only to MULTIPLIED quantities under a square root radical for ADDED 
quantities under a radical. If b2a2 had been under the radical and we had 
had sqrt%28b%5E2a%5E2%29 that would have given b%2Aa but since b2 and a2 are added under 
the radical the rule doesn't work. So step (3) should be:

sqrt%28+b%5E2%2Ba%5E2+%29+=+c+

We cannot take ADDED squared terms from under a square root radical individually
like we can MULTIPLIED squared terms under a square root radical.  So we have
to leave the problem like that. 

Edwin