We have , 21x2−28x+10=0
Comparing the given equation with the general form ax2 + bx + c = 0,
we get a = 21, b = – 28, c = 10
∴ x =

−b±√b2−4ac

2a

=

28±√(−28)2−4×21×10

2×21

=

28±√784−840

42

=

28±√−56

42

=

14±√−14

21

=

14±i√14

21

=

14

21

±

i√14

21

=

2

3

±

i√14

21