1<math xmlns="http://www.w3.org/1998/Math/MathML" display="block"> 2 <mrow> 3 <msub> 4 <mi>P</mi> 5 <mrow> 6 <mi>l</mi> 7 <mo>+</mo> 8 <mn>1</mn> 9 </mrow> 10 </msub> 11 <mfenced> 12 <mrow> 13 <mi>x</mi> 14 </mrow> 15 </mfenced> 16 <mspace width="1em"/> 17 <mo>=</mo> 18 <mspace width="1em"/> 19 <mfrac> 20 <mrow> 21 <mfenced> 22 <mrow> 23 <mn>2</mn> 24 <mi>l</mi> 25 <mo>+</mo> 26 <mn>1</mn> 27 </mrow> 28 </mfenced> 29 <mi>x</mi> 30 <msub> 31 <mi>P</mi> 32 <mi>l</mi> 33 </msub> 34 <mfenced> 35 <mrow> 36 <mi>x</mi> 37 </mrow> 38 </mfenced> 39 <mo>−</mo> 40 <mi>l</mi> 41 <msub> 42 <mi>P</mi> 43 <mrow> 44 <mi>l</mi> 45 <mo>−</mo> 46 <mn>1</mn> 47 </mrow> 48 </msub> 49 <mfenced> 50 <mrow> 51 <mi>x</mi> 52 </mrow> 53 </mfenced> 54 </mrow> 55 <mfenced> 56 <mrow> 57 <mi>l</mi> 58 <mo>+</mo> 59 <mn>1</mn> 60 </mrow> 61 </mfenced> 62 </mfrac> 63 </mrow> 64</math> 65 66