(x的2次方y的2次方-4)(-x的2次方y的2次方-4)-4(xy-2分之1)(xy-2分子1)
=-x的4次方y的4次方+16-4(x²y²-xy+1/4)
=-(xy)的4次方+16-4(xy)²+4xy-1
=-(-2)的4次方+16-4(-2)²-8-1
=-16+16-16-9
=-25
或直接代入计算:
(x的2次方y的2次方-4)(-x的2次方y的2次方-4)-4(xy-2分之1)(xy-2分子1)
=(4-4)(-4-4)-4(-2-1/2)²
=0-4×25/4
=-25