4y^2-2y+5的值为7
4y²-2y=2
2y²-y=1
-2y^2+y+1
=-(2y²-y)+1
=-1+1
=0若代数式3x4-x3+x2-1+kx3中不含x3项，则k=？3x4-x3+x2-1+kx3=3x4+(k-1)x³+x²-1∵不含x3项∴k-1=0k=1