(3a-b+5)(3a+b-5) (要用简便)

问题描述:

(3a-b+5)(3a+b-5) (要用简便)

(3a-b+5)(3a+b-5)=(3a-(b-5))(3a+b-5)=9a^2-(b-5)^2=9a^2-b^2+10b-25

原式=[3a-(b-5)][3a+(b+5)]=9a^2-(b-5)^2=9a^2-b^2+10b-25

=(3a)^2-(b-5)^2
=9a^2-b^2-10b+25