已知M={y|y=x²-4x+3,x∈R},N={y|y=-x²+2x+8,x∈R},求M∩N 答案是{y|-1≤y≤9}
问题描述:
已知M={y|y=x²-4x+3,x∈R},N={y|y=-x²+2x+8,x∈R},求M∩N 答案是{y|-1≤y≤9}
答
y=x*x-4x+3=(x-2)*(x-2)-1>=-1;
y=-x*x+2x+8=-(x-1)*(x-1)+9所以答案为-1