SOLUTION: If a-b=4,ab+c^2+4=0, then find a+b.

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Question 1121201: If a-b=4,ab+c^2+4=0, then find a+b.







Answer by Alex.33(110) About Me  (Show Source):
You can put this solution on YOUR website!
First of all we can easily know a=b+4 <1>. Hence
+%28b%2B4%29%2Ab%2Bc%5E2%2B4=0+
+b%5E2%2Bc%5E2%2B4b%2B4=0+
+%28b%2B2%29%5E2%2Bc%5E2=0+ <2>
Aha! Since
%28b%2B2%29%5E2%3E=0+
c%3E=0+
To make <2> valid both expressions must be equal to zero. Therefore
+c=0+
+b=-2+
And from <1> we know
+a=b%2B4=2+
+a%2Bb=0.+