7v(6) + 4v(54)

Question

Here's my work:

7√(6) + 4√(6 • 9) = 7√(6) + 7√(6) = 14√6

My teacher marked this as wrong on my test, though. What did I do wrong(as I don't see it and can't figure it out)?

Answer 1

7√6 + 4√54

 

= 7√(6) + 4√(9*6)

 

= 7√(6) + 4√9√6

 

You were OK up to here, but then you added 4+3 instead of multiplying them (4*3):

 

= 7√6 + 4*3√6

 

= 7√6 + 12√6

 

= 19√6