Вправи 888 - 1000 » 994 (е)

е) x2 – 4√(x^2 ) – 21 = 0; x2 – 4|x| – 21 = 0; 1) x < 0; x2 + 4x – 21 = 0; D = 42 – 4 • 1 • (–21) = 16 + 84 = 100 = 102; x1 = (-4-10)/2 = (-14)/2 = –7; x2 = (-4+10)/2 = 6/3 = 3 – не задовольняє умову; 2) х ≥ 0; х2 – 4х – 21 = 0; D = (–4)2 – 4 • 1 • (–21) = 16 + 84 = 100 = 102. x1 = (4-10)/2 = (-6)/2 = –3 – не задовольняє умову; х2 = (4+10)/2 = 14/2 = 7. Відповідь: –7; 7.