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2x+y-3=0 x+y-1=0 x-y-3=0 2x-y-5=0
命题“若x>y,则x>|y|”的逆命题 命题“若x>1,则x2>1”的否命题 命题“若x=1,则x2+x-2=0”的否命题 命题“若x2>0,则x>1”的逆否命题
2x-y-5=0 2x+y-3=0 x+y-1=0 x-y-3=0
若y=3,则y′=0 若f(x)=3x+1,则f′(1)=3 若y=-+x,则y′=-+1 若y=sin x+cos x,则y′=cos x+sin x
x-y-3=0 2x+y-3=0 x+y-1=0 2x-y-5=0
若X→Y,Y→Z,则X→Z 若X→Y,Y'Y,则X→Y' 若X→Y,X'X,则X'→Y 若X'X,则X→X'
x﹣y﹣3=0 2x+y﹣3=0 x+y﹣1=0 2x﹣y﹣5=0
若y=3,则y′=0 若f(x)=3x+1,则f′(1)=3 若y=-+x,则y′=-+1 若y=sin x+cos x,则y′=cos x+sin x
若x,y∈R且x2+y2≠0,则x,y全不为0 若x,y∈R且x2+y2≠0,则x,y不全为0 若x,y∈R且x,y全为0,则x2+y2=0 若x,y∈R且xy≠0,则x2+y2≠0
x>0,y>0 x<0,y<0 x>0,y<0 x<0,y>0
x-y+1=0 x+y-1=0 x-y-1=0 x+y+1=0
x-y-3=0 2x+y-3=0 x+y-1=0 2x-y-5=0
if(x==0) y=1; else y=2; if(x==0) then y=1 else y=2; if(x==0) y=1 else y=2; if x==0 y=1; else y=2;
x-2y+1=0 x+2y-3=0 2x+y-3=0 2x-y-1=0
若x2+y2=0,则x,y中至少有一个不为0; 若x2+y2≠0,则x,y中至少有一个不为0; 若x2+y2≠0,则x,y都不为0 若x2+y2=0,则x,y都不为0
命题“若xy=0,则x=0”的否命题为:“若xy=0,则x≠0” “若x+y=0,则x,y互为相反数”的逆命题为真命题 命题“∃x∈R.,使得2x2﹣1<0”的否定是:“∀x∈R.,均有2x2﹣1<0” 命题“若cosx=cosy,则x=y”的逆否命题为真命题
2x+y-3=0 x-2y+1=0 x+2y-3=0 2x-y-1=0