The first-power d ⁡ ⁡ x terms are the highest remaining order. Dividing out the common factor of d ⁡ ⁡ x , and dividing through by the factor ( G + j ω ω C ) , we get Z 0 2 = ( R + j ω ω L ) ( G + j ω ω C ) + Z 0 ( R + j ω ω L ) d ⁡ ⁡ x .