Question

（a加b加c)的平方减（a减b减c)的平方

Answer 1

=(a+b+c+a-b-c)(a+b+c-a+b+c)
=2a(2b+2c)
=4a(b+c)

Answer 2

(a+b+c)^2-(a-b-c)^2=(a+(b+c))^2-(a-(b+c))^2=2*a*(b+c)+2*a*(b+c)=4a(b+c)