Question

$a {}^{2} + (3a - b) \:( 3a + b + b {}^{2} )$

Answer 1

${a}^{2} + (3a - b)(3a + b + {b}^{2} )$
a2+9a2+3ab-3ab-b2+3ab2-b3
a2-b2 +9a2+3ab2-b3

hope it helps you