Which of the following equations have only one solution? Select all correct answers
x²-x-6=0
5x^2 + 20 x + 20 = 0
9x^2 - 25 = 0
4x^2 + 4 x = 0
x^2 + 6 x + 9 = 0

 5x^2 + 20x + 20 = 0 and

x^2 + 6x + 9 = 0

Step-by-step explanation:

x^2 - x - 6 = 0

(x + 2) (x - 3) = 0

x = -2, 3  (two solutions)

5x^2 + 20x + 20 = 0

5(x^2 + 4x + 4) = 0

5 (x + 2)^2

x = -2  (one solution)

9x^2 - 25 = 0

(3x - 5) (3x + 5) = 0

x = +/- 5/3  (two solutions)

4x^2 + 4x = 0

4x (x + 1) = 0

x = 0, -1  (two solutions)

x^2 + 6x + 9 = 0

(x + 3)^2 = 0

x = -3  (one solution)