换元：t＝(3/2)^x,则x＝lnt/ln(3/2),dx＝1/ln(3/2)×1/t dt
(2^x * 3^x)/(9^x－4^x)dx＝1/(t－1/t)×1/ln(3/2)×1/t dt＝1/ln(3/2)×dt/(t^2-1)
套用不定积分公式∫dx/(x^2-a^2)＝1/(2a)×ln|(x-a)/(x+a)|＋C,得原不定积分的结果是
1/ln(3/2)×1/2×ln|(t-1)/(t+1)|＋C＝1/ln(3/2)×1/2×ln|((3/2)^x-1)/((3/2)^x+1)|＋C