Question

$3 x^{2} +21x-90=0$

Answer 1

Решение задания приложено

Answer 2

$3x^2+21x-90=0|:3$
$x^2+7x-30=0$
$D = 7^2-(4*(-30) = 49+120=169=13^2$
$x_{1}= \frac{-7+13}{2} =3$
$x_{2}= \frac{-7-13}{2} =-10$
x1=3;x2=-10