We have,

Now, in order to solve the equation we have to compare this with ax² + bx + c = 0 where a = 21, b = - 28 and c = 10

Thus, the discriminant of the above given equation is:

D = b² – 4ac

= (- 28)² – 4 × 21 × 10

= 784 – 840

= - 56

Hence, the required solutions are:

=

=

=

=