9x2 - 9(a + b)x + (2a2 + 4ab + ab + ab2) = 0
9x2 - (9a + 9b)x + [2a(a + 2b) + b(a + 2b)] = 0
9x2 - (9a + 9b)x + [(a + 2b)(2a + b)] = 0
9x2 - 3[(a + 2b) + (2a + b)]x + {(a + 2b)(2a + b)} = 0
9x2 - 3(a + 2b)x - 3(2a + b)x + {(a + 2b)(2a + b)} = 0
3x[3x - (a + 2b)] - (2a + b)[3x +(a - 2b)] = 0
[3x - (a + 2b)][3x -(2a + b)] = 0
[3x - (a + 2b)][3x - (2a + b)] = 0
[3x - (a + 2b)] = 0
or we can have
[3x - (2a + b)] = 0
3x = (a + 2b) or 3x = (2a + b)
Hence, x = \(\frac{a+2b}{3}\) or x = \(\frac{2a+b}{3}\)