Factorise the expressions. (i) `ax^2 + bx` (ii) `7p^2 + 21q^2` (iii) `2x^3 + 2xy^2 + 2xz^2` (iv) `am^2 + bm^2 + bn^2 + an^2` (v) `(lm + l) + m +1` (vi) `y(y+z) + 9(y+z)` (vii) `5y^2 - 20y - 8z + 2yz` (viii) `10ab + 4a + 5b +2` (ix) `6xy - 4y + 6 - 9x`