(5a-2b)²
=(5a)²-2×(5a)×(2b)+(2b)²
=25a²-20ab+4b²
(2分之m²+2n)²
=(2分之m²)²+2×(2分之m²)×2n+(2n)²
=4分之m的4次方+2m²n+4n²