jQuery animate callback problem

I'm getting an error attempting to change a CSS value on an animate callback. Sorry, I'm a bit new at this. The animate works, but where I insert $('#slide'+prevImage).css('left', '864px') after a comma, I get an error. Is there something wrong with my syntax? Thank you!

My test page:
http://www.dis-hfm.com/default.htm

My Javascript:

$(function(){
	var prevImage=1;
	var nextImage=1;
	var maxImage=5;
	var intervalID=setInterval(slideAnimation,1000);

	function slideAnimation(){
		prevImage=nextImage;
		if (nextImage==maxImage){nextImage=1;} else {nextImage++;}
		$('#slide'+nextImage).animate({left:'-=864px'},{
			$('#slide'+prevImage).css('left', '864px')
		});
	};
});

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