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x-y-3=0 2x+y-3=0 x+y-1=0 2x-y-5=0
x-y-3=0 2x+y-3=0 x+y-1=0 2x-y-5=0
x﹣y﹣3=0 2x+y﹣3=0 x+y﹣1=0 2x﹣y﹣5=0
直线x+y-2=0的左下方 直线x+y-2=0的右上方 直线x+2y-2=0的右上方 直线x+2y-2=0的左下方
的坐标是(1,2),则直线PQ的方程是( ) A.x+2y-3=0 x+2y-5=0 2x-y+4=0 2x-y=0
(1,2),则直线PQ的方程是( ) A.x+2y-3=0 x+2y-5=0 2x-y+4=0 2x-y=0
x2+y2=1(y≠0) x2+y2=4(y≠0) x2+y2=9(y≠0) x2+y2=a2(y≠0)
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-3=0 2x+y-3=0 x+y-1=0 2x-y-5=0
if(x==0)y=l;else y=2; if(x==0)theny=1 elsey=2 if(x=0)y=l else y=2; ifx==0y=1 else y=2;
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;
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