published on: 2015-05-26 12:33:08
i-can-feels.tumblr.com/post/119784774083/
i-can-feels.tumblr.com/post/119795922098/
▲= b² - 4.a.c
i-can-feels.tumblr.com/post/119934823958/
i-can-feels.tumblr.com/post/119972075228/
i-can-feels.tumblr.com/post/120115683553/