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High school mathematics compulsory 5 series question and answer urgent! ! ! ! ! ! ! ! !
The side corresponding to 120 is the longest side, set as a, and the other two sides are A-4 and A-8, then

cos 120 =[(a-4)？ +(a-8)？ -a？ ]/(2(a-4)(a-8))=(a？ -24a+80)/(2(a？ - 12a+32))=- 1/2

And then a? -24a+80=-(a？ - 12a+32)

2a？ -36a+ 1 12=0

Answer? - 18a+56=0

(a-4)(a- 14)=0

A=4 or a= 14.

Pay attention to a-8 > 0

So a= 14

△ area = (1/2) (a-4) (a-8) sin120 = (1/2) ×10× 6× radical (3)/2 =/kloc-0.

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