Let's solve each of these quadratic equations:

1) x^2 - 3x - 40 = 0

Factors of -40 that add up to -3 are -8 and 5.

(x - 8)(x + 5) = 0
x = 8 or x = -5

2) x^2 + 7x + 6 = 0

Factors of 6 that add up to 7 are 1 and 6.

(x + 1)(x + 6) = 0
x = -1 or x = -6

3) x^2 + 6x + 9 = 0

This quadratic equation is a perfect square trinomial.

(x + 3)(x + 3) = 0
x = -3

Therefore, the solutions to the given quadratic equations are:
1) x = 8 or x = -5
2) x = -1 or x = -6
3) x = -3