Question

y²-9x=0 ( cálculo, sem delta)

Answer 1

$y^2-9x=0\\y^2=9x$

$9x=y^2\\x= \frac{y^2}{9}\\x= \frac{y^2}{3^2}\\x=( \frac{y}{3} )^2$

$y^2=9( \frac{y}{3})^2\\y^2=3^2( \frac{y}{3} )^2\\ \sqrt{y^2}= \sqrt{3^2( \frac{y}{3} )^2}\\y=\pm \frac{3y}{3}\\y=\pm y$