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You are watching: The sum of two rational numbers is rational

I recognize this statement is false (if ns am correct) but how to prove it"s false?

"The amount of two rational number is irrational."

2. I understand this declare is true (if ns am correct) however how come prove it"s true?

"The sum of two irrational number is irrational"

I supplied the instance $sqrt2+ sqrt3 = 3.14$

But i may need to use proof by contradiction or contaposition.


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If 2 numbers room rational we deserve to express their sum as$$fracab + fraccd$$which is equal to $$fracad + bcbd.$$Hence, rational.

The amount of two irrational numbers may be irrational. Consider $2+sqrt2$ and also $3+sqrt2$. Both room irrational, and also so is their amount $5+2sqrt2$.


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For one, the comes directly from the closure of addition on $hunterriverpei.combbQ$, but I don"t think that"s the prize they would expect.

Let $a = dfracp_1q_1$ and $b = dfracp_2q_2$ be rationals in $hunterriverpei.combbQ$ and also $q_1, q_2 eq 0$:$$a + b = dfracp_1q_1 + dfracp_2q_2 = dfracp_1q_2 + p_2q_1q_1q_2 in hunterriverpei.combbQ$$

For the 2nd one, how around $dfracsqrt22 + dfracsqrt22 = sqrt2$. A single example is enough to prove the claim.

For bonus points, have the right to you prove that $dfracsqrt22$ is irrational?(Hint: Contradiction. Intend it"s rational, and also use the closure of addition on $hunterriverpei.combbQ$ the was proven.)


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$frac pq$+$frac xz$ $(q,z eq 0)$(by formula of rational numbers).

=$fracpz+qzqz$,which is again in the form $frac ab$ so that is bound to be rational and also $qz$ is no equal to $0$.

Sum that irrational might be irrational is true yet it is always rational if the sum is composed of the irrational number and its an unfavorable and then the amount will yield $0$.Sum of 2 irrational numbers that you expressed together a decimal is no true and only an approximation.


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The amount of 2 irrational number is not necessarily irrational. Because that example, $sqrt2$ and $-sqrt2$ space two irrational numbers, yet their sum is zero ($0$), which subsequently is rational.


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