题目内容

设V是全体平面向量构成的集合,若映射f:V→R满足:对任意向量a=(x1,y1)∈V,b=(x2,y2)∈V,以及任意λ∈R,均有f(λa+(1-λ)b)=λf(a)+(1-λ)f(b)则称映射f具有性质P.先给出如下映射:
①f1:V→R,f1(m)=x-y,m=(x,y)∈V;
②f2:V→R,f2(m)=x2+y,m=(x,y)∈V;
③f3:V→R,f3(m)=x+y+1,m=(x,y)∈V.
其中,具有性质P的映射的序号为______.(写出所有具有性质P的映射的序号)
a
=(x1y1)
b
=(x2y2)
,则λ
a
+(1-λ)
b
=(λx1+(1-λ)x2,  λy1
+(1-λ)y2}
对于①,f[λ
a
+(1-λ)
b
]
=λx1+(1-λ)x2-λy1-(1-λ)y2=λ(x1-y1)+(1-λ)(x2-y2
λf(
a
)+(1-λ)f(
b
)
=λ(x1-y1)+(1-λ)(x2-y2)满足性质P
对于②f2(λa+(1-λb))=[λx1+(1-λ)x2]2+[λy1+(1-λ)y2],λf2(a)+(1-λ)f2(b)=λ(x12+y1)+(1-λ)(x22+y2
∴f2(λa+(1-λb))≠λf2(a)+(1-λ)f2(b),∴映射f2不具备性质P.
对于③f[λ
a
+(1-λ)
b
]
=λx1+(1-λ)x2+λy1+(1-λ)y2+1=λ(x1+y1)+(1-λ)(x2+y2)+1
λf(
a
)+(1-λ)f(
b
)
=λ(x1+y1+1)+(1-λ)(x2+y2+1)═λ(x1+y1)+(1-λ)(x2+y2)+1
满足性质p
故答案为:①③
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