Algebra 2 (Geometric Series)
posted by Greg on .
Write (2x+3y)^3 in expanded form
I need a little help as far as how I would begin working this problem out.

im not positively sure bc its been awhile but i think everything in the parenthesis will be raised to the 3:
2^3x^3 + 3^3y^3 giving you
8x^3 + 27y^3 
To expand this you need to recall Pascal's Triangle, and use it to expand
(a+b)^3 = a^3 + 3a^2b + 3ab^2 + b^3
You have a=2x and b=3y, so you end up with
(2x)^3 + 3(2x)^2(3y) + 3(2x)(3y)^2 + (3y)^3
= 8x^3 + 24x^2y + 54xy^2 + 27y^3