Evaluate this algebraic expression f(a,b)

[epsi00]

I do not have access to the math calculators.
Δ = 162*(a-b)*(a^2-b^2)*(a^3-b^3) -108*(a^3-b^3)*(a-b)^3 + 81*(a-b)^2*(a^2-b^2)^2 - 108*(a^2-b^2)^3 - 27*(a^3-b^3)^2

thanks

 

[haruspex]

Take out some factors to make t simpler. 9 is obvious. (a-b) is another (twice). Several terms have other factors in common, so combine those first.

 

[willem2]

I do not have access to the math calculators.

really?

http://www.wolframalpha.com/input/?i=162*%28a-b%29*%28a^2-b^2%29*%28a^3-b^3%29+-108*%28a^3-b^3%29*%28a-b%29^3+%2B+81*%28a-b%29^2*%28a^2-b^2%29^2+-+108*%28a^2-b^2%29^3+-+27*%28a^3-b^3%29^2

 

[epsi00]

really?

http://www.wolframalpha.com/input/?i=162*%28a-b%29*%28a^2-b^2%29*%28a^3-b^3%29+-108*%28a^3-b^3%29*%28a-b%29^3+%2B+81*%28a-b%29^2*%28a^2-b^2%29^2+-+108*%28a^2-b^2%29^3+-+27*%28a^3-b^3%29^2

Thank you very much. I really did not know that we could use the Wolfram site.