Question

Sabendo que (5, x, 125) forma uma PG determine o x

Answer 1

$a_1=5 \\ a_2=x \\ a_3=125 \\ \\ \frac{a_2}{a_1} =\frac{a_3}{a_2} \\ \\ \frac{x}{5} = \frac{125}{x} \\ \\ x^2=5.(125) \\ x^2=625 \\ x=\pm \sqrt{625} \\ x=\pm \sqrt{5^2.5^2} \\ x=\pm25$