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A PE 4 = CU B PE 6 = CU C PE 8 SI 1 PE A +1 PE B +1 PE C =13 PE 144  URGENT 

Răspuns :

Si trebuie sa afli a, b si c?
[tex] \frac{a}{4} = \frac{b}{6} = \frac{c}{8} [/tex]

[tex]\frac{1}{24} + \frac{1}{36} + \frac{1}{48}=\frac{13}{144}[/tex]

[tex] \frac{a}{4} = \frac{b}{6}[/tex]⇒[tex]6a =4b[/tex]⇒[tex]a= \frac{4}{6} b= \frac{2}{3} b[/tex]

[tex] \frac{b}{6} = \frac{c}{8} [/tex]⇒[tex]6c =8b [/tex]⇒[tex]c= \frac{8}{6} b= \frac{4}{3} b[/tex]

[tex]\frac{1}{a} + \frac{1}{b} + \frac{1}{c} = \frac{13}{144} [/tex]

⇒[tex]\frac{1}{ \frac{2}{3}b } + \frac{1}{b} + \frac{1}{ \frac{4}{3} b} = \frac{13}{144} [/tex]

⇒[tex]\frac{3}{ 2b} } + \frac{1}{b} + \frac{3}{4b} = \frac{13}{144} [/tex]

⇒[tex]\frac{3*2+4+3}{ 4b} = \frac{13}{144} [/tex]⇒[tex]\frac{13}{ 4b} = \frac{13}{144} [/tex]

⇒[tex] 13*144=13*4*b[/tex]⇒[tex]b= \frac{13*144}{13*4} = \frac{144}{4} =36[/tex]

[tex]a= \frac{2}{3} b= \frac{2}{3} *36=2*12=24[/tex]

[tex]c= \frac{8}{6} b= \frac{4}{3} b=36* \frac{4}{3} =12*4=48[/tex]

Verificare:
[tex]\frac{1}{24} + \frac{1}{36} + \frac{1}{48} = \frac{6+4+3}{144} =\frac{13}{144}[/tex]