Question

Encontre o valor "x", pelo Teorema de Tales

Answer 1

Veja...

$\frac{x-1}{x+3} = \frac{3}{9} \\ \\ 9(x-1)=3(x+3) \\ \\ 9x-9=3x+9\\ \\ 9x-3x=9+9 \\ \\ \\ 6x=18 \\ \\ x=18\div6 \\ \\ x=3$

Answer 2

x - 1 = 3
------ -----
x + 3 = 9


3x +9 = 9x - 9

3x - 9x = -9 - 9

-6x = -18

x = -18/-6

x = 3