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Prove root 7 is irrational

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Prove root 7 is irrational
  • 2 answers

Sneha Singh 6 years, 10 months ago

Let root 7 be a rational number Then, =√7 = a/b Now by squaring both side = (√7)² = (a/b)² = 7 = a²/b² = 7b² = a². (A²= 7b² from above) Here 7 divides a² Therefore 7 also divides a Now let a= 7c where c is some integer By squaring both sides = A² = 49c² = 7b² = 49c² = B² = 7c² Here 7 divides b² Therefore 7 also divides b Here a and b both have common factor 7 So our contradiction was wrong , Therefore √7 is irrational

Honey ??? 6 years, 10 months ago

First assume it that it is a rational number then your contradiction will be wrong and then you will prove it that it is irrrational and you can see in your book
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