Proof that x√y is irrational if x is rational and √y is irrational
Assumptions:
Let's assume the following:
- x is a rational number.
- √y is an irrational number.
Proof:
We can prove that x√y is an irrational number by contradiction.
Let's assume that x√y is a rational number. This means that we can express it in the form of a fraction where the numerator and denominator are integers and the denominator is not equal to zero.
Therefore, we can say that:
x√y = a/b
where a and b are integers, and b ≠ 0.
We can now square both sides of the equation to get:
x²y = a²/b²
Since x² is a rational number and y is an irrational number, we know that x²y is an irrational number.
On the other hand, a²/b² is a rational number because a and b are integers.
This creates a contradiction because we have shown that x²y is irrational and a²/b² is rational. Therefore, our assumption that x√y is rational must be false.
Conclusion:
From the above proof, we can conclude that if x is rational and √y is irrational, then x√y is irrational.