ГДЗ Алгебра 9 клас Істер НУШ

3) (3x + 2)(3x – 2) = x + 6;
9x2 – 4 – x – 6 = 0; 9x2 – x – 10 = 0;
D = (–1)2 – 4 • 9 • (–10) = 1 + 360 = 361.
x1 = (1 - √361)/(2 • 9) = (1 - 19)/18 = (-18)/18 = –1;
x2 = (1 + 19)/18 = 20/18 = 10/9 = 11/9.
Відповідь: –1; 11/9.
4) x(x – 2) – (x + 1)2 = x2 – 2x;
x2 – 2x – (x2 + 2x + 1) = x2 – 2x;
x2 – 2x – x2 – 2x – 1 – x2 + 2x = 0;
–x2 – 2x – 1 = 0|• (–1);
x2 + 2x + 1 = 0; (x + 1)2 = 0;
x + 1 = 0; x = –1.
Відповідь: –1.