How do I correctly combine the following

Question

(7a^3 (8ab^6)^(1/2))-(7b^3(18a^7)^(1/2))

Answer 1

(7a ³(8ab ⁶)^1/2-(7b³ (18a ⁷)^1/2

 

7a ³*2*2 ^1/2* a ^1/2 * b ³ - 7b ³ * 3*2 ^1/2 a ^7/2

= 7 a ^7/22 ^5/2 b ³ - 21* 2 ^1/2 a ^7/2 b ³

= -7 sqrt 2 ( a ^7/2 b ³ )

Answer 2

7a³(8ab⁶)^1/2 - 7b³(18a⁷)^1/2

7a³(8^1/2a^1/2b³) - 7b³(18^1/2a^7/2)

7√(8)a^7/2b³ - 7√(18)a^7/2b³

7a^7/2b³(√8 - √18)       √18 = √9√2 = 3√2

 

7a^7/2b³(√8 - 3√2)