CHO HÌNH BÌNH HÀNH ABCD, G LÀ TRỌNG TÂM ABD . CHỌN KHẲNG ĐỊNH...

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^ABD

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^{GA GB GC}

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^

^

^

^

^

^

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^

^

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^

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^

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^

^

^

^

^

^

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^

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^

⁰

^{GA GC GD}

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^

^

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^{GA GB GD}

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^

^

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^{GB GC GD}

^

^

^

⁰





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1

2

2

1

CI



CA



CB

CI

























































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CA



























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CB

6

3

3

6

A.

B.

3

1

1

1

2

6

C.

D.