(2m+1-3n)(2m-1+3n)=?

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(2m+1-3n)(2m-1+3n)=?
(2m+1-3n)(2m-1+3n)=?

(2m+1-3n)(2m-1+3n)=?
(2m+1-3n)(2m-1+3n)
=[2m+(1-3n)][2m-(1-3n)]
=(2m)^2-(1-3n)^2
=4m^2-(1-6n+9n^2)
=4m^2-1+6n-9n^2

=[2m+(1-3n)][2m-(1-3n)]
=(2m)²-(1-3n)²
=4m²-1+6n-9n²