初二数学~求救``

-3a^4b^2 - 6a^3b^3 + 9a^2b^4
=-3a^2b^2(a^2+2ab-3b^2) "对括号内的式子用十字相乘法分解为(a+3b)(a-b)"
原式=-3a^2b^2(a+3b)(a-b)

-3a^4b^2 - 6a^3b^3 + 9a^2b^4=-3a^2b^2(a^2+2ab+b^2)

-3a^4b^2 - 6a^3b^3 + 9a^2b^4
=-3a^2b^2(a^2+2ab-3b^2)
==-3a^2b^2(a+3b)(a-b)

-3a^4b^2-6a^3b^3+9a^2b^4
=-3a^2(4b^+6a1.5-3a2b^2)

-3a^4b^2 - 6a^3b^3 + 9a^2b^4 =3a^2b^2(3b^2-a^2-2ab)
对括号内的式子用十字相乘法得3a^2b^2[(3b+a)(b-a)]
=3a^2b^2(3b+a)(b-a)

-3a^4b^2 - 6a^3b^3 + 9a^2b^4
=-3a^2b^2(a^2+2ab-3b^2)提公因式
=-3a^2b^2(a+3b)(a-b)十字相乘法