proper indentation of very long latex formulae

[walkerlala]

I have tried many measures, but I still can't properly indent a very long latex formulae so that it looks better:

This is a img I cut from one of my blog. As you can see, the formulae is too long to fix in the frame.

I try to put two \linebreak before the = mark. But now it look like this:

which still tastes not so good.

Ideally, I would like it to be something like this:

Is this possible on upmath.me ?

Thanks!

[parpalak]

This question is not related to my editor. It's about LaTeX.

In such cases I split equations "by hands". Here is an example:

[walkerlala]

Thanks, but adding \begin{align*} and \end{align*} doesn't seem to work sometimes. For example, how do you align this?

https://tex.s2cms.ru/g/%7B%5Cpartial%20E%20%5Cover%20%5Cpartial%20y_o%7D%0A%20%26%3D%20%7B%7B%5Cpartial%20%7B%7B1%20%5Cover%202%7D%20%5Cdisplaystyle%5Csum_%7Bk%3D1%7D%5Eq%20(y_%7Bd%2Ck%7D-y_k)%5E2%7D%20%5Cover%20%5Cpartial%20y_o%7D%0A%20%26%3D%20%7B1%20%5Cover%202%7D%20%5Cdisplaystyle%5Csum_%7Bk%3D1%7D%5Eq%20%7B%5Cpartial%20(y_%7Bd%2Ck%7D-y_k)%5E2%20%5Cover%20%5Cpartial%20y_o%7D%0A%20%26%3D%20%7B1%20%5Cover%202%7D%20%5Cdisplaystyle%5Csum_%7Bk%3D1%7D%5Eq%20%7B%7B%5Cpartial%20(y_%7Bd%2Ck%7D-y_k)%5E2%20%5Cover%20%5Cpartial%20y_k%7D%5Ccdot%7B%5Cpartial%20y_k%20%5Cover%20%5Cpartial%20y_o%7D%7D%5C%5C%0A%20%26%3D%20-%20%5Cdisplaystyle%5Csum_%7Bk%3D1%7D%5Eq%20(y_%7Bd%2Ck%7D-y_k)%20%5Ccdot%20%7B%5Cpartial%20y_k%20%5Cover%20%5Cpartial%20y_o%7D%0A%20%26%3D%20-%20%5Cdisplaystyle%5Csum_%7Bk%3D1%7D%5Eq%20e_k%20%5Ccdot%20%7B%5Cpartial%20y_k%20%5Cover%20%5Cpartial%20y_o%7D

I try to add \begin{align*} and \end{align*} , but that doesn't seem to work.

Thanks for you help again.

[parpalak]

There is a syntax error: an extra opening bracket '{'. I've fixed it:

[walkerlala]

Thanks you very much!!