Question 625401

Multiply and simplify showing all your steps. Please help my book does not show how to do these,
1. Square root of 15b times square root of 3b
And 2. (2-square root6)(1+square root of 6) 
Please help one these two I'm not sure how to do them.
 thank you. 


{{{sqrt(15b) * sqrt(3b)}}} ---- {{{sqrt(45b^2)}}} ---- {{{sqrt(3^2*5*b^2)}}} ---- {{{highlight_green(3b*sqrt(5))}}}


{{{(2 - sqrt(6))(1 + sqrt(6))}}}
{{{2 - sqrt(6) + 2sqrt(6) - (sqrt(6))^2}}} ----- Foiling binomials
{{{2 + sqrt(6) - 6}}} ----- {{{highlight_green(- 4 + sqrt(6))}}}


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