1)(5m+4n) (4n-5m)=16n²-25m²

2)(9a²-½m3c)•(9a²+½m³c)=81a⁴ - ¼c²m⁶

3)(7x-3y)²=49x² - 42xy+9y²

4)(1,25a² +8b)²=25a⁴+20a²b+64b²

16