Question

Prove 6+√2 is irrational​

Answer 1

Answer:

Prove that 6 + √2 is an irrational number.

Answer:

Given 6 + √2

To prove: 6 + √2 is an irrational number.

Proof:

Let us assume that 6 + √2 is a rational number.

So it can be written in the form a/b

6 + √2 = a/b

Here a and b are coprime numbers and b ≠ 0

Solving

6 + √2 = a/b

we get,

=> √2 = a/b – 6

=> √2 = (a-6b)/b

=> √2 = (a-6b)/b

This shows (a-6b)/b is a rational number.

But we know that √2 is an irrational number, it is contradictsour to our assumption.

Ask

Question

Our assumption 6 + √2 is a rational number is incor

6 + √2 is an irrational number

ence, proved.

Answer 2

6 is rational, so prove that √2 is irrational and your job is done

suppose √2 is a rational number. Then we can write it √2 = a/b where a, b are whole numbers, b not zero.

We additionally assume that this a/b is simplified to lowest terms, since that can obviously be done with any fraction. Notice that in order for a/b to be in simplest terms, both of a and b cannot be even. One or both must be odd. Otherwise, we could simplify a/b further.

From the equality √2 = a/b it follows that 2 = a2/b2, or a2 = 2 · b2. So the square of a is an even number since it is two times something.

From this we know that a itself is also an even number. Why? Because it can't be odd; if a itself was odd, then a · a would be odd too. Odd number times odd number is always odd. Check it if you don't believe me!

Okay, if a itself is an even number, then a is 2 times some other whole number. In symbols, a = 2k where k is this other number. We don't need to know what k is; it won't matter. Soon comes the contradiction.

If we substitute a = 2k into the original equation 2 = a2/b2, this is what we get:

2 = (2k)2/b2

2 = 4k2/b2

2*b2 = 4k2

b2 = 2k2

This means that b2 is even, from which follows again that b itself is even. And that is a contradiction!!!

WHY is that a contradiction? Because we started the whole process assuming that a/b was simplified to lowest terms, and now it turns out that a and b both would be even. We ended at a contradiction; thus our original assumption (that √2 is rational) is not correct. Therefore √2 cannot be rational