SOLUTION: Find the value of (b+c+d)/2 for the following system: 2b - (c + d) = 10 c + d = - 2b - 2

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Question 1131109: Find the value of (b+c+d)/2 for the following system:
2b - (c + d) = 10
c + d = - 2b - 2
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

Find the value of %28b%2Bc%2Bd%29%2F2+for the following system:
2b+-+%28c+%2B+d%29+=+10.........eq.1
+c+%2B+d++=+-+2b+-+2.........eq.2
------------------------------------------add eq.1 and eq.2
2b+-+%28c+%2B+d%29%2B%28+c+%2B+d+%29+=+10-+2b+-+2
2b+-+cross%28%28c+%2B+d%29%29%2Bcross%28%28+c+%2B+d+%29%29+=+8-+2b+
2b++=+8-+2b+
2b+%2B2b+=+8
4b+=+8
b+=+2

go to
2b+-+%28c+%2B+d%29+=+10.........eq.1..substitute b
4-+%28c+%2B+d%29+=+10
+-+%28c+%2B+d%29+=+10-4
+-+%28c+%2B+d%29+=+6...both sides multiply by -1
+%28c+%2B+d%29+=+-6


then
%28b%2B%28c%2Bd%29%29%2F2+=%282%2B%28-6%29%29%2F2=%282-6%29%2F2=-4%2F2=-2