(3a²-4a+5）（3a²+4a-5）-a²（9a²-16）=[3a²-(4a-5)][3a²+(4a-5）]-a²(9a²-16)=9a^4-(4a-5)²-9a^4+16a²=16a²-(4a-5)²=(4a+4a-5)(4a-4a+5)=5(8a-5)=40a...