Giải thích các bước giải:

 Ta có : 

$\text{MN}$$\parallel$$\text{AC}$

Do:

$\text{AB}$$\bot$$\text{AC}$

$\Rightarrow$ $\text{MN}$$\bot$$\text{AB}$

Mà $\text{AM}$$\bot$$\text{BN}$

$\Rightarrow$$\text{M}$ là trực tâm của $\triangle$$\text{ABN}$

$\Rightarrow$$\text{BM}$$\bot$$\text{AN}$

$\Rightarrow$$\widehat{AKM}$ = $\widehat{MHB}$$(=90^o)$

Mà $\widehat{AMK}$ = $\widehat{BMH}$

$\Rightarrow$$\triangle$$\text{KMA}$ = $\triangle$$\text{HMB}$$\text{(g.g)}$

$\Rightarrow$$\dfrac{MA}{MB}$ =$\dfrac{MK}{MH}$

$\Rightarrow$$\text{MB . MK = MA . MH}$

$\Rightarrow$$\text{4MB . MK =2MA . 2MH}$

$\Rightarrow$$\text{4MB . MK =}$ $AH^2$

$\text{kienhoang504599}$