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If x2 + 8y2 + 12y - 4xy + 9 =...

This question belongs to Arithmetic Ability Algebra
Algebra
?

If x2 + 8y2 + 12y - 4xy + 9 = 0, then the value of (7x + 8y) is:

Answer & Solution
Correct Answer: Option A
x2 + 8y2 + 12y - 4xy + 9 = 0
x2 + 4y2 - 4xy + 4y2 + 12y + 9 = 0
(x - 2y)2 + (2y + 3)2 = 0
x = 2y
2y = -3
y = $$\frac{{ - 3}}{2}$$
x = -3
(7x + 8y)
= 7 × (-3) + 8 × $$\left( {\frac{{ - 3}}{2}} \right)$$
= -21 - 12
= -33
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