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Mathematics 18 Online
Pixel:

http://prntscr.com/hbc04f

Rainluke01:

1,2,4

563blackghost:

A rational number is where it is a whole number or a decimal with repeating decimal such as 3.222222... and fractions (that either end nicely or repeat). A. Shows \(\bf{\sqrt{11} \times \sqrt{5} = \sqrt{11 \times 5} = \sqrt{55}}\) This would not be rational since the square root equals `7.416198487...`

Rainluke01:

i thought it was anynumber that was not whole

563blackghost:

Irrational is `any number that can not be a rational number` such as \(\bf{\pi}\), \(\bf{\sqrt{8}}\), \(\bf{-\sqrt{11}}\) etc.

563blackghost:

Rational are either repeated decimals, some fractions (that either end repeated or end nicely), and whole numbers.

Rainluke01:

oh

563blackghost:

B. \(\bf{\sqrt{9} \times \sqrt{16} = \sqrt{9 \times 16} = \sqrt{144}}\) The \(\bf{\sqrt{144}}\) squares easily to `12` so this is rational.

Pixel:

5rad4 is C?

563blackghost:

Not quite. \(\bf{\sqrt{2} \times \sqrt{2} = 2}\) So we end up with \(\bf{5 \times 2 =10}\)

Pixel:

10 is rational

563blackghost:

yup

Pixel:

d is rational?

563blackghost:

Well if we did \(\bf{3} \times \sqrt{2} = \sqrt{6}\) we have no term that squares perfectly from 6, so no.

Pixel:

oof im bad at radicals

563blackghost:

Sorry meant \(\bf{\sqrt{3}}\)

563blackghost:

Do you know your perfect squares?

Pixel:

i have a list of only 16

563blackghost:

You can identify your perfect squares by taking a number and raising it to the power of 2. \(\bf{1^{2}=1}\) \(\bf{2^{2}=4}\) \(\bf{3^{2}=9}\) \(\bf{4^{2}=16}\) \(\bf{5^{2}=25}\) \(\bf{6^{2}=36}\) so on and so forth...

563blackghost:

For example let us say we have \(\bf\sqrt{54}\). We list the terms of `54` to see if it contains a perfect square. `54:1,2,3,6,9,18,27,54,` We see that it has `9` which is perfect, and we multiply `9` by `6` to get 54. So we turn it into this... \(\large\bf{\sqrt{54} \rightarrow \sqrt{9 \times 6}}\) Now we know that `9` is perfect but to what? Well it is `3` since it squares to this the term will be placed on the outside. \(\large\bf{\sqrt{9 \times 6} \rightarrow 3\sqrt{6}}\) This is the rational form of \(\bf{\sqrt{54}}\).

563blackghost:

Do you kinda get the explanation?

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