Question 44259
{{{a(a+5)(a-5)}}}
{{{a(a+5)(a-5)}}}
Use FOIL (first, outers, inners, lasts) to add the products of the expressions in the brackets.
If you had to multiply (a+b) by (c+d), using FOIL you would get:
{{{(a+b)(c+d)=ac+ad+bc+bd}}}
so {{{(a+5)(a-5)=a^2 -5a +5a -25}}}
Now {{{a(a+5)(a-5)=a(a^2 -5a +5a -25)}}}
{{{a(a+5)(a-5)=a(a^2  -25)}}}
{{{a(a+5)(a-5)=a^3  -25a)}}}

I hope this helps
P.S. I am trying to start up my own homework help website. I would be extremely grateful if you would e-mail me some feedback on the help you received to adam.chapman@student.manchester.ac.uk