The expression is .
(The product of two same signs is positive)
(Apply additive identity property: )
The product is 0.
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.![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=51b221d009f87efbee1454b88c5389c4.png\")
(The product of two same signs is positive)![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=27826b958946345374624f5bab2ff9ca.png\")
(Apply additive identity property: ![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=d9a330057101303b4e61d20418b2f2a0.png\")
)![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/solution.JPG\")