已知（x+y）2＝4，（x-y）2＝3，试求xy的值

更新时间2022-08-16 01:32:13

(x+y)²＝4

(x-y)²＝3

(x+y)²-(x-y)²=4xy

4xy=4-3=1

xy=1/4

3x (x + 2 )+( x+1 )( x -1 ) = 4( x²+8 )

3x²+6x+x²-1=4x²+32

6x=33

x=5.5

x=3.5/2,y=0.5/2

x=33/6