a^2（a^2-1）-6
=a^4-a^2-6
=(a^2-3)(a^2+2)
=(a-√3)(a+√3)(a^2+2)
(x^2-1)(x^2+2)-70
=x^4+x^2-2-70
=x^4+x^2-72
=(x^2-8)(x^2+9)
=(x-2√2)(x+2√2)(x^2+9)第一題是b哦a^2（a^2-1）-b=a^4-a^2-b=a^4-a^2+1/4-1/4-b=(a^2-1/2)^2-(1+4b)/4當(dāng)b<-1/4時無法在實(shí)數(shù)范圍內(nèi)分解=[a^2-1/2+√(1+4b)/2][a^2-1/2-√(1+4b)/2]=[a^2-1/2+√(1+4b)/2][a^2-1/2-√(1+4b)/2]當(dāng)b>0時第一個括號無法在實(shí)數(shù)范圍內(nèi)分解=(a^2-√(1-√(1+4b))/2)(a^2+√(1-√(1+4b))/2)(a^2-√(1+√(1+4b))/2)(a^2+√(1+√(1+4b))/2)