prove that √5 is an irrational number
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Answer:
it's example is given in class 10th ncert book
chapter 1
veryeasy
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Nice I can prove
Just write as I write this question includes lots of statements
A rational no. is. no. which is in the form of p/q where p and q have no common factor and q is not equal to 0
Let √5 be assumed as a rational no.
so
√5= p/q
Squaring both sides
(√5)² = p²/q²
5= p²/q²
Cross Multiplying both sides
p²= 5q²
As 5 divides 5q²
it will also divide p²
so 5 will divide p
Let p=5k(where k is an integer)
squaring both sides
p²= 25k²
5q²= 25k²
q²=25k²/5
q² = 5k²
Since 5 divides 5k²
it will also divide q²
since it divides q² it will divide q too
Thus p and q have common factor 5 .This contradicts our assumption that p and q have no common factor ( except 1)
Therefore√5 is an irrational no.