Răspuns :

Deci, ΔAMN≡ΔABC⇒[tex] \frac{MN}{BC} [/tex] = [tex] \frac{AN}{AC}= \frac{AM}{AB} [/tex] 
[tex]= \frac{4}{12}= \frac{4}{AB}= \frac{3}{AC} [/tex]  
[tex] \frac{1}{3}= \frac{4}{AB} [/tex]⇒ AB = 4×3÷1=12 
[tex] \frac{1}{3}= \frac{3}{AC} [/tex]⇒ AC = 3×3÷1=9 
STIM URMATOARELE DATE: AB=12 AM=4 MN=4 AN=3 BC=12 AC=9 
AB= AM+MB⇒MB=AB-AM=12-4=8⇒ MB=8
AC=AN+NC⇒NC=AC-AN=9-3=6⇒NC=6
P trapezului BCNM= BC+CN+MN+MB= 12+6+4+8= 30
P BCNM= 30 cm 

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