Question

bạn nào giúp mk vs ạ!!

tính hợp lí:

A= 2005⁴-2004.2006.(2005²+1)

B=1999.(2000²+2001)-2001.(2000²-1999)

Answer 1

A= 2005⁴-2004.2006.(2005²+1)

=\(2005^4-\left(2005-1\right)\cdot\left(2005+1\right)\cdot\left(2005^2+1\right)\)

=\(2005^4-\left(2005^2-1\right)\cdot\left(2005^2+1\right)\)

=\(2005^4-\left(2005^4-1\right)\)

=1

Answer 2

B=1999.(2000²+2001)-2001.(2000²-1999)

=\(1999\cdot2000^2+1999\cdot2001-2001\cdot2000^2+2001\cdot1999\)

=\(2000^2\left(1999-2001\right)+2\cdot1999\cdot2001\)

=\(2000^2\cdot\left(-2\right)+2\cdot1999\cdot2001\)

=\(2000^2\cdot\left(-2\right)+2\left(2000-1\right)\left(2000+1\right)\)

=\(-2\cdot2000^2+2\left(2000^2-1\right)\)

=\(-2\cdot2000^2+2\cdot2000^2-2\)

=-2