Question

已知(a+b)^2=4,(a-b)^2=6,求4ab的值

Answer 1

a+b)�0�5=a�0�5+b�0�5+2ab=4
(a-b)�0�5=a�0�5+b�0�5-2ab=6
AB=6-4=2 4AB=8

Answer 2

.(a+b)�0�5=a�0�5+b�0�5+2ab=4
(a-b)�0�5=a�0�5+b�0�5-2ab=6
(a+b)�0�5-(a-b)�0�5=4ab=-2

Answer 3

(a+b)�0�5=a�0�5+b�0�5+2ab=4
(a-b)�0�5=a�0�5+b�0�5-2ab可知4AB=-2

Answer 4

(a+b)^2=4a^2 + 2ab + b^2=4 (a-b)^2=6a^2 - 2ab + b^2=6 4ab = -2 两式相减