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  • Usuário do Brainly
2014-09-03T16:25:27-03:00
A)
 \frac{70}{x} = \frac{315}{2x+5}

multiplica cruzado

315x=140x+350

315x-140x=350

x= \frac{350}{175}

\fbox{$x=2$}

b)

 \frac{x}{x-2} + \frac{3}{x+2} = \frac{x^2+1}{x^2-1}

mmc=x²-4  (x+2)(x-2)

x(x+2)+3(x-2)=x^2+1

x^2+2x+3x-6=x^2+1

x^2+2x+3x-6-x^2-1=0

cancela x² com -x²

2x+3x=1+6

5x=7

\fbox{$x= \frac{7}{5}$}
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