Question

两道计算题(过程详细点)(1).(a^2+a-4)(a^2-a-4)(2).(x-2y-1)^2

Answer 1

(1).(a^2+a-4)(a^2-a-4)

=[(a^2-4)+a][(a^2-4)-a]

=(a^2-4)^2-a^2

=a^4-8a^2+16-a^2

=a^4-9a^2+16

(2).(x-2y-1)^2

=[(x-2y)-1]^2

=(x-2y)^2-2(x-2y)+1

=x^2-4xy+4y^2-2x+4y+1