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Homework Statement
Please check that the proof is correct or not.
Let ℝ+ = {x[itex]\inℝ[/itex]: x>0} and T = {x[itex]\inℝ[/itex]: 0<x<1}.
Let x∈ℝ+ and t∈T
Prove: If x[itex]\leq [/itex]xt then x[itex]\leq [/itex]1.
* You may assume any common properties of log(x) as well as : if 0<a[itex]\leq b[/itex] then log(a) ≤ log(b)
Any help is appreciated.
Homework Equations
The Attempt at a Solution
First, I assume the theorem is false, so negation of If x[itex]\leq [/itex]xt then x[itex]\leq [/itex]1 is true.
The negation of the theorem is: x[itex]\leq [/itex]xt [itex]\wedge[/itex] x>1
x[itex]\leq [/itex]xt [itex]\wedge[/itex] x>1 Premis
x[itex]\leq [/itex]xt Inference rule for conjunction
log(x) ≤ log(xt) log both side
log(x) ≤ t*log(x) properties of log
1 ≤ t
which is a contradiction with the domain of t since 0<t<1
Therefore, the negation of If x[itex]\leq [/itex]xt then x[itex]\leq [/itex]1 is false
Thus, If x[itex]\leq [/itex]xt then x[itex]\leq [/itex]1
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