Вправи 1001 - 1100 » 1076

1076. Знайди корені квадратного тричлена. a) 4x2 + 3x – 1; x = (-3 ± √(9+16))/8 = (-3 ±5)/8; x1 = –1; x2 = 0,25; б) 6x2 + 7x – 5; x = (-7 ± √(49-4 •6 •(-5)))/12 = (-7 ±5)/12; x1 = (-20)/12 = –5/3 = –12/3; x2 = 1/2; в) –x2 – 4x + 5; x1 = –5; x2 = 1; г) 9x2 + 6x + 1; (3x + 1)2; x = –1/3; ґ) –4x2 + 5x – 2; D = 25 – 4 • (–4) • (–2) = 25 – 32 < 0; коренів немає; д) 0,4x2 + 0,7x – 3; x = (-0,77 ± √(0,49+4,8))/0,8 = (-0,7 ±2,3)/0,8; x1 = (-30)/8 = –33/4; x2 = 2.