Question

化简求值：3x²y-6xy-8xy-4+x²y+1，其中=－

Answer 1

解：原式=3x²y+x²y-6xy-8xy-4+1
=4x²y+2xy+1
=－时：原式=4(-)²y+2×(-)y+1
="y-y+1"
=1 

先合并同类项，再代入求值。