If a2 + b2 + 49c2 +18 = 2(b + 28c - a), then the value of (2a - b + 7c) is:
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Correct answer: D
Explanation
The correct answer is option 4 i.e. 1
a2 + b2 + 49c2 +18 = 2(b + 28c - a)
a2 + b2 + 49c2 +18 = 2b + 56c - 2a
a2 + b2 + 49c2 +18 = 2b + 56c - 2a
(a2 + 2a + 1) + (b2 - 2b + 1) + (49c2 - 56c + 16) = 0
(a + 1)2 + (b - 1)2 + (7c - 4)2 = 0
a + 1 = 0, b - 1 = 0, 7c - 4 = 0
a = -1, b = 1, c = 4/7
(2a - b + 7c) = [2(-1) - 1 + 7(4/7)] = -2 - 1 + 4 = 1