设y=kx+bx=0,y=by=0,x=-b/k1/2*|b|*|-b/k|=5b²=10*|k|p：b=5k-4(5k-4)²=10|k|k≥0,25k²-40k+16=10kk=1.6或k=0.4b=4或b=-2y=1.6x+4或y=0.4x-22）k＜025k²-40k+16=-10k无解