Question

Resolva:

x (x-1)=9-x

Answer 1

$x(x - 1) = 9 - x \\ \\ x {}^{2} - x = 9 - x \\ \\ x {}^{2} - x + x - 9 = 0 \\ x {}^{2} - 9 = 0 \\ \\ x {}^{2} = 9 \\ \\ \sqrt{ {x}^{2} } =± \sqrt{9} \\ \\ x = ± \: 3$