The expression is .
The product two same signs is positive.
The product two opposite signs is negative.
The value of expression is .
![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step1.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=23aecab5b3c77e78d17cc4659233c40b.png\")
.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=a538629f9f67e12af0fdbb10d48183ca.png\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=1bd7783314f9377d5f9cb6adf3a4f28a.png\")
![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/solution.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=c731a69153df44ed83b4c7d4ca7586a1.png\")
.