2) А) x²-11X-42=0
a= 1, b= -11, c= -42
D=b²-4ac= 121-4*1*(-42)=121+168=289 √289= 17
X1= 11+17 /2 = 28/2 = 14
X2= 11-17 /2 = -6/2 = -3
Б) -2x²-5X-2=0
a= -2, b= -5, c= -2
D=25-4*(-2)*(-2)=25-16= 9 √9= 3
X1= 5+3 /-4 = 8/-4 = -2
X2=5-3 /-4 = 2/-4 = -1/2 или -0.5
В) x^4 -13x²+36=0
a= 1, b= -13, c= 36
D= 169-4*1*36= 169-144= 25 √25 = 5
X1= 13+5 /2 =18/2 = 9
X2= 13-5 /2 = 8/2 = 4