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ANSWER

EXPLANATION
We use the method of completing the squares.
The equation is

We rewrite the above equation to obtain;

We divide through by 3 to obtain;

We add half the coefficient of

to both sides of the equation to get,

The right hand side is now a perfect square.

We now take square root of both sides to get;

We add -2 to both sides,

We simplify to obtain,
Answer:
Sum of interior angles of polygon = (n-2)*180
1) Pentagon:
2)Hexagon:
3) Heptagon:
4) Octagon:
Answer:X is any number more than 7
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