SSC CGL Model Paper 19

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Question : 58 of 100

Marks: +1, -0

If

9a^2 + 4b^2 + c^2 + 21

= 4(3a + b -2x)

, then the value of

(7a + 13b- 17c)

is

$78 1/6$
$79 1/6$
$77 1/6$
$75 1/6$

Solution:

(3a) ^2 + (2b) ^2 + c^2-

2 (6 a )-2 (2 b )

+ 2(4c) + 21 = 0

(3a- 2) ^2 + (2b -1 ) ^2

+ (c + 4) ^2 = 0

3a = 2 = a = 2 /3

;

2b = 1 = b = 1/2

;

c = -4 = c = -4

;

⇒7×2/3+13×1/2+17×4

=79 1/6

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