Ответ:

1) 4х² - 20 = 0

4(х²-5)= 0

х²=5

х = ±√5

2) 3х²+5х=0

х(3х+5)=0

3х+5=0

3х= -5

х= -5/3

3) х²-5х-24=0

а = 1; b= -5; c= -24

D = b²-4ac = (-5)²-4*1*(-24) = 25 + 96 = 121

x1 = (5+11)/2= 16/2 = 8

x2 = (5-11)/2 = -6/2 = -3

4)7x²-22x+3= 0

a = 7; b = -22; c = 3

D = 484- 4*7*3 = 484 -84= 400

x1 = (22+20)/14 = 42/14 = 3

x2= (22-20)/14 = 2/14 = 1/7

5)7x²-6x+2=0

D= 36-4*7*2 = 36-56= -20, коренів немає

6) 4x²+12x+9= 0

a=4 b= 12 c= 9

D= 144-4*4*9 = 144-144= 0

x = -12/8 = -1.5

номер 2

x1+x2 = 6

x1*x2 = 4

x²-6x+4=0