已知x+y=-3,xy=1试求(2x+1)(2y+1)的值

2x+1)(2y+1)

=4xy+2x+2y+1
=4xy+2(x+y)+1
=4*1+2*(-3)+1
=-1

(2x+1)(2y+1)
=4xy+2y+2x+1
=4xy+2(x+y)+1
=4×1+2×(-3)+1
=4-6+1
=-1

=4xy+2y+2x+1
=4xy+2(x+y)+1
=4×1+2×(-3)+1 =-1

乘起来展开就好了阿。4xy+2x+2y+1.…太简单了撒

(2x+1)(2y+1)=4xy+2(x+y)+1
因为x+y=-3,xy=1代入上式，得
(2x+1)(2y+1)=4xy+2(x+y)+1=4*1+2*(-3)+1=4-6+1=-1