Prove that √5 is irrational...........
Answers
we can prove this by indirect proof
let's assume that the number√5 is rational..... (1)
that is,
it can be denoted in fractional or p/q form
therefore,
√5=p/q
therefore
√5q=p
but on LHS,
number is irrational and on RHS number is rational....(2)
statement(2) is contradictory to (1)
therefore our assumption is wrong.
hence proved that,
√5 is irrational
to prove root 5 is irrational ...
lets assume root 5 as rational
so.. root 5 = p/q
where p and q are co-prime number
root 5 = p/q
by squaring both the sides
5 = (p/q)^2
5= p^2 /q^2
q^2 = p ^2 / 5 ........(1)
by eqn (1) we get to know that ..
p^2 is divisible by 5
so p is also divisible by 5
now consider p = 5m
so .. by putting value in (1)
q^2 = (5m)^2 / 5
q ^2 = 25 m ^2 / 5
q ^2 = 5 m^2
q ^2 /5 = m ^2 ......(2)
by eqn (2) we get to know that
q^2 is divisible by 5
so q is also divisible by 5
therefore by eqn (1) and (2) we can say that p and q have factor more than two numbers . and hence they are not co-prime number
since our assumption was wrong and it contradict the fact thatt root 5 is irrational
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