LaTeX equation is always on one page

I have a very large equation of the form

\begin{align}

I(a,b) &= \int_{[a,b]} x^d\lambda (x) \\

&= \frac{1}{10^b a!}\int_{[a,b]} x^6\lambda (x)

\end{align}

The only difference is, my equation does not only have one line under the top equation but about 10. The thing is that my TeX program always wants that all these equations appear on one page. This is of course problematic, because the preceding page looks very stretched and almost empty cause I waste that much space. Therefore I want that it should be possible that this equation is written over two pages. How can I do this?

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use \allowdisplaybreaks before the alignment –  David Carlisle Jul 20 '14 at 0:50
thanks....that did exactly what I wanted –  Xin Wang Jul 20 '14 at 1:54
You don't have those blank lines in the actual code, have you? –  egreg Jul 20 '14 at 10:43
no, I don't.... –  Xin Wang Jul 20 '14 at 15:16