a)[tex] \frac{3}{5} = \frac{x}{10} =\ \textgreater \ 3*10=5x=\ \textgreater \ x=30:5=6[/tex]
b)[tex] \frac{7}{x}= \frac{21}{15} =\ \textgreater \ 7*15=21x=\ \textgreater \ x= \frac{105}{21} =5[/tex]
c)[tex] \frac{x+2}{x+7} = \frac{3x+6}{48} =\ \textgreater \ 48*(x+2)=(x+7)*(3x+6)=[/tex]= 3x²+6x+21x+42= 3x²+27x+42
Δ=27²-4*3*42=729-504=225
x1=[tex] \frac{-27- \sqrt{225} }{2*3} = \frac{-27-15}{6} = \frac{-42}{6} =-7[/tex]
x2=
