If you are referring to the following picture:

![enter image description here][1]

which you have uploaded in [the first revision](https://math.stackexchange.com/posts/938196/revisions) of [this post](https://math.stackexchange.com/questions/938196/when-equality-holds-in-an-inequality), I do not think the problem was that the picture was too small. The problem was mainly that it had a large blank area, so it was scaled to fit the area for the question. If you cut from the picture only the relevant part, it is more readable:

![enter image description here][2]

Feel free to copy the clipped picture to your question, if you think it improves your post. (But I think that the current version, where all the content of the picture was reproduced, does no lack anything after omitting the picture.)

I should point out that:

 * This is only relevant to the third part of your question. If you post the question about posting an image as a separate question, I will delete my post here and move it to the new post.
 * I am not really sure to which extent this answer the third part of your question, since you did not mention any details. (I had to guess which picture you had problems with.)
 * The downvotes did not necessarily come because of the picture. (But it is a reasonable guess.) Another issue with your post is a rather non-descriptive title: *When equality holds in an inequality*. (Although for me this would not be reason enough to downvote, some users might have higher standards.)
 * On the other hand, there are some commendable things about your post. (Perhaps deserving an upvote.) You included the source where the question comes from. You explained which part from that book is exactly the place you have problem with.

  [1]: http://i.stack.imgur.com/52CGl.png
  [2]: http://i.stack.imgur.com/9RPtM.png