How do you simplify: Square root of 7 + square root of 7^2 + square root of 7^3 + square root of 7^4 + square root of 7^5?

Question

2028 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2015-07-24T16:55:42

Here's how you could simplify this expression.

Start by writing your expression

$sqrt(7) + sqrt(7""^2) + sqrt(7""^3) + sqrt(7""^4) + sqrt(7""^5)$

Now, one way in which you can simplify this expression is by using the product property of radicals, which tells you that

$sqrt( a * b) = sqrt(a) * sqrt(b)$

for $a>=0$ and $b>=0$ .

This means that you can write all the numbers that are under the radicals as products of $7""^2$ , starting with

$color(blue)(7""^3 = 7""^2 * 7)$
$color(green)(7""^4 = 7""^2 * 7""^2)$
$color(orange)(7""^5 = 7""^2 * 7""^2 * 7)$

Your expression will become

$sqrt(7) + 7 + color(blue)(sqrt(7""^2 * 7)) + color(green)(sqrt(7""^2 * 7""^2)) + color(orange)(sqrt(7""^2 * 7""^2 * 7))$

$sqrt(7) + 7 + color(blue)(sqrt(7""^2) * sqrt(7)) + color(green)(sqrt(7""^2) * sqrt(7""^2)) + color(orange)(sqrt(7""^2) * sqrt(7""^2) * sqrt(7))$

$sqrt(7) + 7 + color(blue)(7sqrt(7)) + color(green)(7 * 7) + color(orange)(7 * 7 * sqrt(7))$

$sqrt(7) + 7 + 7sqrt(7) + 49 + 49 sqrt(7)$

Now simply add the terms that do not contain a radical and the terms that do contain a radical separately to get

$(7 + 49) + (sqrt(7) + 7sqrt(7) + 49sqrt(7)) = 56 + 57sqrt(7)$

Alternatively, you can simplify this expression by grouping some of these terms together and factorizing all but the first term. This will get you

$sqrt(7) + (sqrt(7""^2) + sqrt(7""^3)) + (sqrt(7""^4) + sqrt(7""^5))$

$sqrt(7) + sqrt(7""^2) * (1 + sqrt(7)) + sqrt(7""^4) * (1 + sqrt(7))$

This is equivalent to

$sqrt(7) + (1 + sqrt(7)) * (sqrt(7""^2) + sqrt(7""^4))$

$sqrt(7) + (1 + sqrt(7)) * (7 + 49)$

$sqrt(7) + (1 + sqrt(7)) * 56$

$sqrt(7) + 56 + 56 * sqrt(7)$

Once again, the result will be

$56 + 56sqrt(7) + sqrt(7) = 56 + 57sqrt(7)$