15.
(2022高一上·黔東南期中)
已知
的定義域?yàn)?img class="mathml" src="http://math.21cnjy.com/MathMLToImage?mml=%3Cmath+xmlns%3D%22http%3A%2F%2Fwww.w3.org%2F1998%2FMath%2FMathML%22%3E%3Cmn%3E%5B%3C%2Fmn%3E%3Cmo%3E%E2%88%92%3C%2Fmo%3E%3Cmn%3E1%3C%2Fmn%3E%3Cmn%3E++%EF%BC%8C+%3C%2Fmn%3E%3Cmn%3E2%3C%2Fmn%3E%3Cmn%3E%5D%3C%2Fmn%3E%3C%2Fmath%3E" style="max-width:100%;vertical-align: middle;"> , 則
的定義域?yàn)?span id="dq4arst" class="filling" >.