If a2 + 49b2 + c2 + 18 = 2 (28b - c - a) then the value of (a + 7b - c) is:
Show answer & explanation
Correct answer: D
Explanation
The correct answer is Option 4 i.e. 4.
Given that
a2 + 49b2 + c2 + 18 = 2 (28b - c - a)
a2 + 1 + 2a + 49b2 + 16 - 56b + c2 + 1 + 2c = 0
(a + 1)2 + (7b - 4)2 + (c +1)2 = 0
a = -1
b = 4/7
c = -1
Put these values in (a + 7b - c)
= -1 + 7 * (4/7) + 1 = 4