Multiply : \( (9x^2 + 25y^2 + 15xy + 12x – 20y + 16) \) by \( (3x – 5y + 4) \)

\[ (9x^2 + 25y^2 + 15xy + 12x – 20y + 16)(3x – 5y + 4) \] \[ = 27x^3 – 45x^2y + 36x^2 + 75xy^2 – 125y^3 + 100y^2 + 45x^2y – 75xy^2 + 60xy \] \[ \quad + 36x^2 – 60xy + 48x – 60xy + 100y^2 – 80y + 48x – 80y + 64 \] \[ = 27x^3 – 125y^3 – 180xy + 64 \]