(1)已知(1－2x)⁷＝a₀＋a₁x＋a₂x²＋…＋a₇x⁷，那么a₁＋a₂＋…＋a₇＝________．

(2)若(x²＋x－1)ⁿ＝a₀＋a₁(x－1)＋a₂(x－1)²＋…＋a_2n(x－1)²ⁿ，則a₀＋a₁＋a₂＋…＋a_2n＝________．

(3)(x²－2x＋3)ⁿ＝a₀＋a₁x＋a₂x²＋…＋a_2n－1x^2n－1＋a_2nx²ⁿ，則a₀＋a₂＋a₄＋a_2n－2＋a_2n＝________．