evaluate:-
(2x-5y)^3-(2x+5y)^3
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(2x-5y)³-(2x+5y)³
a³-b³ = (a-b)(a²+b²+ab)
=> (2x-5y-2x-5y)[{2x-5y}²+{2x+5y}²+(2x-5y)(2x+5y)]
=> -10y(4x²+25y²-20xy+ 4x²+25y²+20xy+4x²-25y²)
(a+b)(a-b) = a²-b²
-10y(12x²+25y²)
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