Use the substitution y = 3x + 1 to solve for x :

5(3x + 1)² + 6(3x + 1) - 8 = 0.

Find the values of x if p + 1 = 0 and x² + px - 6 = 0.

If x = p is a solution of the equation x(2x + 5) = 3, then find the values of p.

If x = 3 is a solution of the equation (k + 2)x² - kx + 6 = 0 , find the value of k. Hence, find the other root of the equation.