Question

a的3次方加a的2次方减a减1等于啥

Answer 1

a^3+a^2-a-1
=(a^3-1)+(a^2-a)
=(a-1)(a^2+a+1)+a(a-1)
=(a-1)(a^2+2a+1)
=(a-1)(a+1)^2