+55 You can re-write the expression to be ((2a-3b)^2)^2. First, you can simplify the inside by using the square of binomials formula: (a+b)^2=a^2+2ab+b^2
This gives 4a^2-12ab+9b^2. Then you can multiply each term, and get a really big number: 16a^4 - 96a^3*b + 216a^2*b^2 - 216ab^3 + 81b^4
