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Aflati numarul natural x , astfel incat fiecare dintre urmatoarele egalitati sa fie adevatate: a) 3/5=x/10. b) 7/x=21/15. c) x+2/x+7=3x+6/48. ("/" inseamna supra)

Răspuns :

a)×=3•10/5=6
b)×=7•15/21=5
produsul mezilor =produsul extremilor
a)
3/5=x/10→5*x=3*10→x=30/5→x=6
b)
7/x=21/15→21x=7*15→x=105/21→x=5
c)
(x+7)(3x+6)=48(x+2)→3x^2+6x+21x+42=48x+96→3x^2+27x-48x=96-42→3x^2-21x=54→
x(3x-21)=54→x=9