ANSWER
1. No solution
2. 4 and 6
3. 81
EXPLANATION
1. The given quadratic equation is

This implies that:

There is no real number whose square is negative one.
This quadratic equation has no solution.
2. The given quadratic equation is

We split the middle term with -6,-4 because their product is 24 and their sum is -10

We factor by grouping


We have x=4 and x=6.
3. The given quadratic equation is

We the square of half the coefficient of x to both sides of the equation.

The correct choice is C.