Sorry, but (1 x)(1 y) doesn't make any mathematical sense with just blank spaces between the 1's and the letters x and y. Did you mean (1+x)(1+y)? or this (1+x)(1-y)? or this (1-x)(1-y)? or this (1/x)(1+y)? or this (1+x)(1/y)? or this (1+x)(1-y)? or this (1/x)(1-y)? etc.? etc.? ??????????????????? Edwin