y=x²-(k+3)x+k
=x²-kx-3x+k
=x²-3x+(1-x)k
当x=1时,1-x=0,
y=1²-3×1+0×k=-2
所以,无论k为何值二次函数y=x²-(k+3)x+k的值都经过点（1,-2）.