<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
.shows{
display: none;
}
</style>
</head>
<body>
<label for="check">
<input type="checkbox" name="check" id="check" value="1" />
<span>启用输入框</span>
</label>
<br /><br />
<div class="shows">
公式：<input type="text" name="texts" id="texts" placeholder="请输入..."/>
</div>
<script src="js/jquery-1.12.4.min.js" type="text/javascript" charset="utf-8"></script>
<script type="text/javascript">
$(function(){
$("#check").click(function(){
var check = this.checked;
if (check){
$('.shows').slideDown().show();
}else{
$('.shows').slideUp().hide();
}
})
})
</script>
</body>
</html>
效果预览：