Polynomial identities

How many of these are valid identities

5k^2+5 = (k-2) + (2k+1) ^2

m^3-1 = (m-1) (1+m+m^2)

(x+2) ^2 + (x+2) = (x+2) (x+3)

5k² + 5 = (k - 2) + (2k + 1) ²

5k² + 5 = (k - 2) + (2k + 1) (2k + 1)

5k² + 5 = (k - 2) + (4k² + 2k + 2k + 1)

5k² + 5 = (k - 2) + (4k² + 4k + 1)

5k² + 5 = 4k² + 5k - 1

- 4k² - 4k²

k² + 5 = 5k - 1

+ 1 + 1

k² + 6 = 5k

k² - 5k + 6 = 0

k = - (-5) + / - √ ((-5) ² - 4 (1) (6))

2 (1)

k = 5 + / - √ (25 - 24)

2

k = 5 + / - √ (1)

2

k = 5 + / - 1

2

k = 5 + 1 k = 5 - 1

2 2

k = 6 k = 4

2 2

k = 3 k = 2

m³ - 1 = (m - 1) (1 + m + m²)

m³ - 1 = m + m² + m³ - 1 - m - m²

m³ - 1 = m - m + m² - m² + m³ - 1

m³ - 1 = m³ - 1

(x + 2) ² + (x + 2) = (x + 2) (x + 3)

(x + 2) (x + 2) + (x + 2) = x² + 3x + 2x + 6

(x² + 2x + 2x + 4) + (x + 2) = x² + 5x + 6

(x² + 4x + 4) + (x + 2) = x² + 5x + 6

x² + 4x + x + 4 + 2 = x² + 5x + 6

x² + 5x + 6 = x² + 5x + 6

The first problem isn't a valid identity; the last two problems are.