问题
解答题
分解因式
(1)7x2-21x
(2)3a2-3b2
(3)x2-x-6 (十字相乘法)
(4)a4-8a2b2+16b4.
答案
(1)7x2-21x=7x(x-3);
(2)3a2-3b2=3(a2-b2)=3(a+b)(a-b);
(3)x2-x-6=(x-3)(x+2);
(4)a4-8a2b2+16b4=(a2-4b2)2=(a+2b)2(a-2b)2.
分解因式
(1)7x2-21x
(2)3a2-3b2
(3)x2-x-6 (十字相乘法)
(4)a4-8a2b2+16b4.
(1)7x2-21x=7x(x-3);
(2)3a2-3b2=3(a2-b2)=3(a+b)(a-b);
(3)x2-x-6=(x-3)(x+2);
(4)a4-8a2b2+16b4=(a2-4b2)2=(a+2b)2(a-2b)2.