解:
(1)①$(3×5)^{2}=15^{2}=225,$$3^{2}×5^{2}=9×25=225;$
②$[(-2)×3]^{2}=(-6)^{2}=36,$$(-2)^{2}×3^{2}=4×9=36;$
③$[(-3)×(-4)]^{2}=12^{2}=144,$$(-3)^{2}×(-4)^{2}=9×16=144;$
(2)$(ab)^{2}=a^{2}b^{2},$$(ab)^{3}=a^{3}b^{3},$$(ab)^{n}=a^{n}b^{n}$($n$为正整数);
(3)$(-8)^{2025}×(0.125)^{2025}=(-8×0.125)^{2025}=(-1)^{2025}=-1$