方程2n+y=1和3y-1=2y+1的解相同,则n的值是______.
解方程3y-1=2y+1得:y=2
把y=2代入方程2n+y=1得:2n+2=1
解得:n=-12.
A.当溶液中c(CH3COO-)=c(Na+)时,醋酸与氢氧化钠恰好完全反应
B.当溶液中c(CH3COO-)=c(Na+)时.一定是氢氧化钠过量
C.当溶液中c(CH3COO-)=c(Na+)>c(H+)=c(OH-)时,一定是醋酸过量
D.当溶液中c(Na+)>c(CH3COO-)>c(OH-)>c(H+)时,一定是氢氧化钠过量
一Have you handed in your schoolwork yet?
一Yes,I have.I guess it _____ now.
A.has graded
B.is graded
C.is being graded
D.is grading