Question

Найдите корни квадратного трехчлена: 1)х^2-10х+9 2)5х^2+12х+4

Answer 1

1) x²-10x+9 = 0
    a =1; b = -10; c=9
    D = b²-4ac
    D = (-10)²- 4 ·9 = 100 -  36 = 64(√64=8)
    x1 = -b+√D/2a ⇒ -(-10)+8/2 = 18/2 = 9.
    x2 = -b-√D/2a ⇒ -(-10) -8/2 = 2/2 = 1.
2) 5x²+12x+4 = 0
    a=5; b=12; c=4
    D = b²-4ac
    D = 12² - 4·5·4 = 144 - 80 = 64 (√64=8)
    x1 = -b+√D/2a ⇒ -12+8/2·5 = -4/10 = -0,4.
    x2 = -b-√D/2a ⇒ -12-8/2·5 = -20/10 = -2.