Question

设集合A=｛x│x的平方-3x-10≤0｝集合B=｛x│x的平方+ax-2a的平方≤0｝如果B包含于A,求实数a的取值范

Answer 1

x^2 - 3x -10 = 0

x1 = 5,x2 = -2

A={ x | -2 =< x =< 5 }

x^2 + ax - 2a^2 = 0

x1 = a,x2 = -2a

B包含于A,且题中未给出a的正负性,有

-2 =< a,-2a =< 5 ( a < 0 ) 或 -2 =< -2a,a =< 5 ( a >= 0 )

-2 =< a =< 1