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Daca a,b,c ∈ N si ab + ca = 715 , calculati 18a(5b + 5c)

Răspuns :

ab+ca=715
a*(b+c)=715
18a*(5b+5c)=
=18a*5*(b+c)=
=18*5*a*(b+c)=
=90*715=64350


18a(5b + 5c) = 5·18a(b+c) = 90·(ab + ac ) = 90 · 715 = 64 350