Beth is correct answered.
Since liz did not considered the exponent in thirs step.
Therefore beth is correct.
Beth is correct answer.
![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step1.JPG\")
![\"\"](\"/test/fckeditor/editor/plugins/fckeditor_wiris/integration/showimage.php?formula=d1622611fc88fa0fbe88f093bcb90f93.png\")
in thirs step.![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/solution.JPG\")