Разложите на множетели квадратный трехчлена:

1) x^2-3x-18;

2) 7x^2-8x+1;

3) 5x^2+8x+3;

4) 80x^2-32x+3

1) x^2-3x-18=0

D=9+72=81

x1 = (3-9) / 2 = - 3

x2 = (3+9) / 2=6

x^2-3x-18 = (x+3) (x-6)

2) 7x^2-8x+1=0

D/4=16-7=9

x1 = (4-3) / 7=1/7

x2 = (4+3) / 7=1

7x^2-8x+1 = (x-1/7) (x-1)

3) 5x^2+8x+3=0

D/4=16-15=1

x1 = (-4-1) / 5 = - 1

x2 = (-4+1) / 5 = - 3/5

5x^2+8x+3 = (x+1) (x+3/5)

4) 80x^2-32x+3=0

D/4=256-240=16

x1 = (16-4) / 80=3/20

x2 = (16+4) / 80=1/4

80x^2-32x+3 = (x-3/20) (x-1/4)