急！！！！！！分解因式3a^3+7a^2-4

3a^3+7a^2-4
=3a^3+3a^2+4a^2-4
=3a^2(a+1)+4(a+1)(a-1)
=(a+1)(3a^2+4a-4)
=(a+1)(3a-2)(a+2)

3a^3+7a^2-4
=(3a^3+3a^2)+(4a^2-4)
=3a^2(a+1)+4(a^2-1)
=3a^2(a+1)+4(a+1)(a-1)
=(a+1)[3a^2+4(a-1)]
=(a+1)(3a^2+4a-4)
=(a+1)(a+2)(3a-2)

3a^3+7a^2-4
=3a^3+3a^2+4a^2-4
=3a^2(a+1)+4(a+1)(a-1)
=(a+1)(3a^2-4a-4)
=(a+1)(3a+2)(a-2)

3a^3+7a^2-4=3a^3+3a^2+4a^2-4
=3a^2(a+1)+4(a+1)(a-1)
=(a+1)(3a^2+4a-4)
=(a+1)(a+2)(3a-2).

过程大概是这样的
3a^3+7a^2-4
=3a^3+3a^2+4a^2-4
=3a^2(a+1)+4(a+1)(a-1)
=(a+1)(3a^2+4a-4)
=(a+1)(3a-2)(a+2)
祝你学习进步

3a^3+7a^2-4
=3a^3+3a^2+4a^2+4-8
=3a（a^2+1）+4（a^2+1）-8
=（3a+4）（a^2+1）-8