Question

Помогите с алгеброй, 15 баллов даю!!

Answer 1

$7x^{2}+21x-(x+3)=0\\\\7x^{2}+21x-x-3=0\\\\7x^{2}+20x-3=0\\\\D=20^{2}-4*7*(-3)=400+84=484=22^{2}\\\\x_{1}=\frac{-20-22}{14}=-\frac{42}{14}=-3\\\\x_{2}=\frac{-20+22}{14}=\frac{1}{7}\\\\\boxed{x_{1}=-3 \ ; \ x_{2} =\frac{1}{7}}$

Answer 2

Смотри...............................