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in trapezul abcd ,AB paralel CDEF]este linia mijlocie .daca EF=7cm si AB=9cm.sa se afle CD

Răspuns :

EF = [tex] \frac{B+b}{2} = \frac{AB+CD}{2} = \frac{9+CD}{2} [/tex]
7 = [tex] \frac{9+CD}{2} [/tex]
7·2 = 9 + CD
14 = 9 + CD
CD = 14 - 9
CD = 5 cm