1若x2-y2=100, x+y= -25,则x-y的值是( )
A.5 B. 4 C. -4 D. 以上都不对
2、化简(m2+1) (m+1)(m-1) -(m4+1)的值是( )
A. -2m2 B. 0 C.-2 D.-1
3、若|x+y-5|+(x-y-3)2=0,则x2-y2的结果是( )
A.2 B.8 C.15 D.无法确定
4、计算(x-y)(-y-x)的结果是( )
A.-x2+y2 B. -x2-y2 C. x2-y2 D. x2+y
5、设(3m+2n)2=(3m-2n)2+P,则P的值是( )
A.12mn B. 24mn C.6mn D.48mn