bài tập toán lớp 8

T

thinhrost1

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$\dfrac{AE}{AB} + \dfrac{AF}{AC}=\dfrac{AE}{AB}+\dfrac{DE}{AC}= \dfrac{AE}{AB}+\dfrac{BE}{AB}=1$ (đpcm)
 
R

ronaldover7

Áp dụng dl talet
$\frac{AF}{AC}$=$\frac{DE}{AC}$=$\frac{BD}{BC}$
CMTT $\frac{AE}{AB}$=$\frac{DF}{AB}$=$\frac{DC}{BC}$
\Rightarrow $\frac{AF}{AC}$+$\frac{AE}{AB}$=$\frac{BD}{BC}$+$\frac{DC}{BC}$=1
 
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