prove that √3 is an irrational number
Answers
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SHORT FORM:-
Let us assume that root 3 is rational.
Root 3 = a/b where a and b are integers and coprimes.
Root 3 * b = a
Square LHS and RHS
3b2 = a2
b2 = a2/3
Therefore 3 divides a2 and 3 divides a.
Now take ,
a = 3c
Square ,
a2 = 9c2
3b2 = 9c2
b2/3 = c2
Therefore 3 divides b2 and b.
LONG FORM:-
Let us assume that √3 is a rational number.
then, as we know a rational number should be in the form of p/q
where p and q are co- prime number.
So,
√3 = p/q { where p and q are co- prime}
√3q = p
Now, by squaring both the side
we get,
(√3q)² = p²
3q² = p² ........ ( i )
So,
if 3 is the factor of p²
then, 3 is also a factor of p ..... ( ii )
=> Let p = 3m { where m is any integer }
squaring both sides
p² = (3m)²
p² = 9m²
putting the value of p² in equation ( i )
3q² = p²
3q² = 9m²
q² = 3m²
So,
if 3 is factor of q²
then, 3 is also factor of q
Since
3 is factor of p & q both
So, our assumption that p & q are co- prime is wrong
hence,. √3 is an irrational number