Show that the set of positive real numbers form a vector spa
Show that the set of positive real numbers form a vector space under the operation x+y=xy and ax=x^a All ten axioms must be verified.
Solution
Checking associativity:
x+(y+z)=x+yz=x(yz)=xyz
(x+y)+z=xy+z=(xy)z=xyz
Checking commutativity
x+y=xy=yx=y+x
Identity element
1 forms the identity
x+1=x*1=x
Inverse element
x+x^{-1}=xx^{-1}=1
So each non zero x has an inverse.
Compatibility of scalar multipliciation with field multiplication
a(bx)=ax^b=(x^b)^a=x^(ab)=(ab)x
Identity of multiplication
1*x=x^1=x
Distributivity of scalar multiplication w.r.t vector addition
a(x+y)=a(xy)=(xy)^a=x^ay^a=x^a+y^a=ax+ay
Distributivity of scalar multiplication with respect to field addition
(a+b)x=x^(a+b)=x^ax^b=x^a+x^b=ax+bx
