Question

Решите уравнение 21х2-4х-1=0

Answer 1

42x-4x-1=0
38x-1=0
38x=1
x=1:38

Answer 2

d=b^2-4ac=100
√d=10>0 2 решения
x1= (4+10)/42=7/21
x2=(4-10)/42=-3/21