Question #1 - I dont understand the last step which is = (3a +1) √a

Question

√9a^3 + √a

= √9 √a² · a + √a
= 3√a² · √a + √a
= 3a√a + √a
= (3a +1) √a


Question #2 - again I dont understand how from√9² x² + 9² to √9² (x² +1)

√81x² +81

= √9² x² + 9²
= √9² (x² +1)
= 9√x² + 1

Thanks :)

Answer 1

= 3a√a + √a
= √a(3a + 1) , √a is a common factor

√9² x² + 9²
= 9x^2 + 81
= 9(x^2 + 9)

the step from = √9² x² + 9²
to √9² (x² +1) is incorrect