知集合A={xlx=a^2+2a-3,a∈R},B={yly=x^2+3x+b,x∈R}是否存在b,使得B是A的真子使得B是A的真子集，若存在，将b写成集合，若不存在，请说明理由存在，因为x=a^2+2a-3=(a+1)^2-4>=-4,所以A={xlx>=-4};又因为y=(x+3/2

知集合A={xlx=a^2+2a-3,a∈R},B={yly=x^2+3x+b,x∈R}是否存在b,使得B是A的真子使得B是A的真子集，若存在，将b写成集合，若不存在，请说明理由存在，因为x=a^2+2a-3=(a+1)^2-4>=-4,所以A={xlx>=-4};又因为y=(x+3/2
知集合A={xlx=a^2+2a-3,a∈R},B={yly=x^2+3x+b,x∈R}是否存在b,使得B是A的真子
使得B是A的真子集，若存在，将b写成集合，若不存在，请说明理由
存在，因为x=a^2+2a-3=(a+1)^2-4>=-4,所以A={xlx>=-4};又因为y=(x+3/2)^2+b-9/4>=b-9/4,故若要使B是A的真子集，则b-9/4>-4,即b>-7/4.如果不明白可再问
请问为什么因为x=a^2+2a-3=(a+1)^2-4>=-4,所以A={xlx>=-4}？

知集合A={xlx=a^2+2a-3,a∈R},B={yly=x^2+3x+b,x∈R}是否存在b,使得B是A的真子使得B是A的真子集，若存在，将b写成集合，若不存在，请说明理由存在，因为x=a^2+2a-3=(a+1)^2-4>=-4,所以A={xlx>=-4};又因为y=(x+3/2
.写成完全平方的形式就大于等于0啊,然后又有个-4,所以就大于等于-4了

a

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