Вправи 888 - 1000 » 904

904. Розв’яжіть рівняння. а) (x – 1)x + 3x = 0; x2 – x + 3x = 0; x2 + 2х = 0; х(х + 2) = 0; х = 0 або х = –2; б) 2у(у + 5) = 6y; 2у2 + 10y – 6y = 0; 2y2 + 4у = 0; y2 + 2у = 0; у(у + 2) = 0; у = 0 або у = –2; в) (z + 2)(z – 2) = 0; z = –2 або z = 2; г) (x + 2)(x – 2) = 4; x2 – 4 = 4; x2 = 8; x = ±√8; x = ±2√2. ґ) 5x2 + 3x + 7 = 7(x + 1); 5x2 + Зx + 7 – 7x – 7 = 0; 5x2 – 4x = 0; x(5x – 4) = 0; x = 0 або x = 4/5; д) 2(x2 – 1) = (x – 1)(x +1); 2x2 – 2 = x2 – 1; 2x2 – x2 = –1 + 2; x2 = 1; x = 1 а6о x = –1.