1) 3(4-5xy)(4+5xy) = 3(4^2-(5xy)^2) = 3(16-25x^2y^2) = 48-75x^2y^2
2) (x^2-y^3)^2 = (x^2)^2 - 2*x^2*y^3 + (y^3)^2 = x^4 - 2x^2y^3 + y^6
3) (c+m)^2-(c-m)^2 = (c+m-(c-m))(c+m+c-m) = (c+m-c+m)*2c = 2m*2c = 4cm
1) 3(4-5xy)(4+5xy) = 3(4^2-(5xy)^2) = 3(16-25x^2y^2) = 48-75x^2y^2
2) (x^2-y^3)^2 = (x^2)^2 - 2*x^2*y^3 + (y^3)^2 = x^4 - 2x^2y^3 + y^6
3) (c+m)^2-(c-m)^2 = (c+m-(c-m))(c+m+c-m) = (c+m-c+m)*2c = 2m*2c = 4cm