= {(3x + 2z) + (5y)} {(3x + 2z) - (5y)}
= (3x + 2z)2 - (5y)2
{since (a + b) (a - b) = a2 - b2}
= 9x2 + 4z2 + 2 × 3x × 2z - 25y2
= 9x2 + 4z2 + 12xz - 25y2
= 9x2 + 4z2 - 25y2 + 12xz