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<h1 align="center">上标和下标标签</h1>
<h3 align="center">在数字中计算</h3>
<h3 align="center">上标：X<sup>3</sup>+9X<sup>2</sup>-3=0</h3>
<h3 align="center">下标:3X<sub>1</sub>+2X<sub>2</sub>=10</h3>
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