Prove that the product of the two rational numbers sqrt(36) and 5/3 is a rational number. Find the product and explain how you know it is a rational number. Explain your reasoning in 1-2 sentences.

9 answers

To prove that the product of \(\sqrt{36}\) and \(\frac{5}{3}\) is a rational number, we first calculate \(\sqrt{36} = 6\), which is a rational number since it can be expressed as \(\frac{6}{1}\).

Now, we find the product: \[ 6 \times \frac{5}{3} = \frac{6 \times 5}{3} = \frac{30}{3} = 10. \]

Since \(10\) can also be expressed as a fraction \(\frac{10}{1}\), it is a rational number. Therefore, the product of \(\sqrt{36}\) and \(\frac{5}{3}\) is rational because it is expressed as the ratio of two integers (30 and 3).

Prove that the sum of 3/4 and sqrt(10) is irrational. Show your work, and in 1-2 sentences, explain why the sum is an irrational number

To prove that the sum \( \frac{3}{4} + \sqrt{10} \) is irrational, we will use a proof by contradiction.

Assume that the sum \( x = \frac{3}{4} + \sqrt{10} \) is rational. By definition, a rational number can be expressed as the ratio of two integers \( p/q \) where \( p \) and \( q \) are integers and \( q \neq 0 \).

From our assumption: \[ \sqrt{10} = x - \frac{3}{4}. \] Since \( x \) is rational and \( \frac{3}{4} \) is rational, the right-hand side \( x - \frac{3}{4} \) is also rational. This means that \( \sqrt{10} \) is rational as well.

However, \( \sqrt{10} \) is known to be an irrational number since it cannot be expressed as a fraction of two integers. Thus, we reach a contradiction where we assumed that a rational number led to the conclusion that \( \sqrt{10} \) is rational. Therefore, our original assumption that \( \frac{3}{4} + \sqrt{10} \) is rational must be false.

Thus, the sum \( \frac{3}{4} + \sqrt{10} \) is irrational.

In summary, the sum is irrational because assuming it to be rational leads to the false conclusion that \( \sqrt{10} \) is rational, which contradicts the established knowledge that \( \sqrt{10} \) is irrational.

Can you make it shorter

To prove that \( \frac{3}{4} + \sqrt{10} \) is irrational, assume it is rational. Then, we can express it as \( x = \frac{3}{4} + \sqrt{10} \), leading to \( \sqrt{10} = x - \frac{3}{4} \). Since both \( x \) and \( \frac{3}{4} \) are rational, their difference \( \sqrt{10} \) would also have to be rational. However, \( \sqrt{10} \) is known to be irrational, leading to a contradiction.

Thus, \( \frac{3}{4} + \sqrt{10} \) is irrational because it results in the false conclusion that an irrational number is rational.

can you make it look easier

Sure! Here’s a simplified version:

Assume \( \frac{3}{4} + \sqrt{10} \) is rational. This means we can write it as a fraction. If we rearrange, we find:

\[ \sqrt{10} = \left( \frac{3}{4} + \sqrt{10} \right) - \frac{3}{4}. \]

Since both \( \frac{3}{4} \) and \( \left( \frac{3}{4} + \sqrt{10} \right) \) are rational, their difference \( \sqrt{10} \) must also be rational. However, \( \sqrt{10} \) is known to be irrational, so our assumption is wrong.

Therefore, \( \frac{3}{4} + \sqrt{10} \) is irrational because it leads to a contradiction that an irrational number is rational.

what does the left and right indicate

In the equation

\[ \sqrt{10} = \left( \frac{3}{4} + \sqrt{10} \right) - \frac{3}{4}, \]

the left side, \( \sqrt{10} \), represents the expression we are analyzing.

The right side shows the assumption that if \( \frac{3}{4} + \sqrt{10} \) is rational (can be expressed as a fraction), then subtracting the rational number \( \frac{3}{4} \) from it should also yield a rational number. This leads us to conclude that \( \sqrt{10} \) would then also have to be rational.

The contradiction arises because we know \( \sqrt{10} \) is irrational, which shows that our initial assumption—that \( \frac{3}{4} + \sqrt{10} \) is rational—must be incorrect. Thus, it indicates that \( \frac{3}{4} + \sqrt{10} \) is irrational.