Question

а)25x^{2}-16=0,б)3x^{2}-15х=0,в)5x^{2}+20=0

А4.x^{2}-27=0,б)4x^{2}=12

Answer 1

$25x^2-16=0$
$25x^2=16$
$x^2=frac{16}{25}$
$x_1=-sqrt{frac{16}{25}}=-frac{4}{5}$
$x_2=sqrt{frac{16}{25}}=frac{16}{25}$

$3x^2-15x=0$
$3x(x-5)=0;$
1) $3x=0$
$x_1=0$
2) $x-5=0$
$x=0+5$
$x_2=5$

$5x^2+20=0$
$x^2+4=0$
$x^2=-4; -4<0$
действительных решений нет

$x^2-27=0$
$x^2=27$
$x_1=-sqrt{27}=-3sqrt{3}$
$x_2=sqrt{27}=3sqrt{3}$

$4x^2=12$
$x^2=12:4$
$x^2=3$
$x_1=-sqrt{3}$
$x_2=sqrt{3}$