已知（a-1)²+（2a-b)⁴+|a+3c|=0,求a-(b-2c)的值.

平方项、4次方项与绝对值项均恒非负,三者之和=0,三者分别=0
a-1=0
2a-b=0
a+3c=0
解得a=1 b=2 c=-1/3
a-(b-2c)
=a-b+2c
=1 -2 +2×(-1/3)
=-5/3