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How to prove that root p …

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How to prove that root p is a irrational number
  • 1 answers

Sia ? 6 years, 4 months ago

Let us assume, to the contrary, that √p is rational.
So, we can find co-prime integers a and b(b ≠ 0)
{tex}\begin{array}{l}\sqrt p=\frac ab\\\end{array}{/tex}
{tex}a = b _ { \sqrt { P } }{/tex}
on squaring both sides we get
a2 = pb2 ...... (1)
so a2 is divisible by p
hence a is divisible by p ....... (2)
So, we can write a = pc for some integer c.
Squaring both the sides we get
a2 = p2 c2 ....
⇒ pb2 = p2 c2 ....[From (1)]
⇒ b2 = pc2
⇒ b2 is divisible by p
⇒ b is divisible by p ....... (3)
From (2) and (3) we conclude that p divides both a and b.
∴ a and b have at least p as a common factor.
But this contradicts the fact that a and b are co-prime. (As per our assumption)
This contradiction arises because we have assumed that √p is rational.
∴ √p is irrational.

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