Question

已知集合A=(x/X大于等于-2 小于等于a) B（y/y=2x=3,x属于A C (Z/x的平方,x属于A) C是B子

Answer 1

A={x| -2≤x≤a},

B={y| y=2x+3 ,x∈A}

C={z| z=x^2,x∈A}

C= {x| 0≤x≤4 or 0≤x≤a^2 }

B= { x| -1 ≤x ≤ 2a+3 }

C is subset of B,then

4≤2a+3 and 2a+3≥a^2

a≥1/2 and a^2-2a-3≤ 0

a ≤1/2 and -1≤a≤3

=> 1/2≤a≤3