1.(a-2b-3c)^2 2.a^4-(a^2+2b^2)(a^2-2b^2) 3.化简求值(m-3)(m+3)-(m-3)^2其中m=-1

题目

1.(a-2b-3c)^2 2.a^4-(a^2+2b^2)(a^2-2b^2) 3.化简求值(m-3)(m+3)-(m-3)^2其中m=-1

答案

1.原式=a^2+4b^2+9c^2-4ab-6ac+12bc
2.原式=a^4-(a^4-4b^4)=4b^4
3.原式=m^2-9-(m^2-6m+9)=6m-18=-6-18=-24