put formulas on the left position in LateX
===

As you know the following equation will be in the center:


    >$$
    >\sum_{\substack{a\leq1/2\\0<b\leq T}}\frac{2+a}{2|b|}
    >$$

and the following is on the left but in small size and decrease the space

    >$
    >\sum_{\substack{a\leq1/2\\0<b\leq T}}\frac{2+a}{2|b|}
    >$

but the below formula is similar to the first one, but on the left:

    >$
    >\displaystyle{\sum_{\substack{a\leq1/2\\0<b\leq T}}\frac{2+a}{2|b|}}
    >$

does anyone another way such that it works similar to the last one ( put the formula on the left) but with 

    >\begin{xxxx}
    >*
    >\end{xxxx}
     