Given:


this quadratic is easily factored:

what value of X makes the quadratic equal zero?

let x = -7

this is the only value that makes the equation equal to zero.
thus, there is a double root, which is equal to -7
for part 2:
Since it is quadratic, it will always have two roots. This means both roots are equal to -7
generally, whenever a quadratic factors into a perfect square of sums, like:

where 'a' is a constant,
the solution is a double root.
Meaning both roots to the quadratic are equal.