求着两道八下几何题答案
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伦芝兰3v
2017-02-22
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![](https://iknow-pic.cdn.bcebos.com/95eef01f3a292df54d447882b5315c6035a873a6?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
(1)将原式化为:
(a-5)²+(b-12)²+(c-13)²=0
∴a=5 b=12 c=13
∵5²+12²=13²
∴BC⊥AC
∴5/CD=13/12
CD=60/13
![](https://iknow-pic.cdn.bcebos.com/500fd9f9d72a6059416f378d2134349b033bba2e?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto)
(2)
∵5²+12²=13²
∴BC⊥AC
设CD=DE=x BD=y则:
5²+ x²=y²
x²+8²=(12-x)²
24x=12²-8²=80
x=10/3
y²= x²+5²=100/9+25=325/9
y=(5√13)/3
即:BD= (5√13)/3
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