<p>A particle moves in a straight line so that its displacement&nbsp; x at any time&nbsp; t is given by&nbsp;&nbsp;<span class="equation">\(x^2 = 1 + t^2\)</span>. Its acceleration at any time t is&nbsp;<span class="equation">\(x^{-n}\)</span>​​​​​​​ where n = _____</p>