Question 617773
Use Pascal triangle & the binomial Theorem to expand:  (2x-3y)^4   
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The 4th row is 1 4 6 4 1
--> {{{16x^4 + 4*(2x)^3*(-3y) + 6*(2x)^2*(-3y)^2 + 4*(2x)*(-3y)^3 + 81y^4}}}
= {{{16x^4 - 96x^3y + 216x^2y^2 - 216xy^3 + 81y^4}}}