两道因式分解,急啊!4^9a^2b+8^7ab-16^4ab(x^2-4x)^2-2(x^2-4x)-15

Question

两道因式分解,急啊!
4^9a^2b+8^7ab-16^4ab
(x^2-4x)^2-2(x^2-4x)-15

Answer 1

4^9a^2b+8^7ab-16^4ab
=(2^2)^9a^2b+(2^3)^7ab-(2^4)^4ab
=2^18a^2b+2^21ab-2^16ab
=2^18a^2b+2^16ab(2^5-1)
=2^18a^2b+31*2^16ab
=2^16ab(2^2a+31)
=2^16ab(4a+31);
(x^2-4x)^2-2(x^2-4x)-15
=[(x^2-4x)-5][(x^2-4x)+3]
=(x^2-4x-5)(x^2-4x+3)
=(x-5)(x+1)(x-1)(x-3).