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Giải thích các bước giải:

a.Xét $\Delta BED,\Delta ADC$ có:

$\widehat{DBE}=\widehat{CBx}=\widehat{BAD}=\widehat{CAD}$

$\widehat{BDE}=\widehat{ADC}$

$\to \Delta DBE\sim\Delta DAC(g.g)$

$\to \widehat{BED}=\widehat{ACD}$

$\to \widehat{AEB}=\widehat{ACD}$

Mà $\widehat{EAB}=\widehat{DAC}$

$\to \Delta ABE\sim\Delta ADC(g.g)$

b.Xét $\Delta EBD,\Delta EAB$ có:

Chung $\hat E$

$\widehat{EBD}=\widehat{BAD}=\widehat{EAB}$

$\to \Delta EDB\sim\Delta EBA(g.g)$

$\to \dfrac{ED}{EB}=\dfrac{EB}{EA}$

$\to EB^2=ED.EA$