# Math Is Fun Forum

Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫  π  -¹ ² ³ °

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## #1 2021-08-29 13:38:28

XaiDiv
Member
From: Antarctica
Registered: 2021-08-22
Posts: 25

### help omg :'(

hey guys, how can I calculate the value of

√(1-a) / √(1+a) - √(1+a) / √(1-a) ?

(a = 1 / √5 fyi.)

Hellooooooooooooo

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## #2 2021-08-29 19:13:15

Bob
Registered: 2010-06-20
Posts: 9,428

### Re: help omg :'(

hi XaiDiv

If you collect the two fractions over a common denominator you'll get:

square this and divide by a squared to get

Then substitute the given value and you're there.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

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## #3 2021-08-29 23:26:36

XaiDiv
Member
From: Antarctica
Registered: 2021-08-22
Posts: 25

### Re: help omg :'(

Thank you bob!!! this might sound a bit weird but could you write out the solution step-by-step all the way to the end? I'm having a bit of trouble understanding why the numerator is -2a.

Hellooooooooooooo

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## #4 2021-08-30 19:23:49

Bob
Registered: 2010-06-20
Posts: 9,428

### Re: help omg :'(

so

If a = 1/root(5) then

There are two values for k; +1 and -1.  We need to investigate which fits the original expression.

so

So the value k = -1 is the one we want.

Bob

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

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## #5 2021-08-30 21:35:00

XaiDiv
Member
From: Antarctica
Registered: 2021-08-22
Posts: 25

### Re: help omg :'(

tysm bob <3

Hellooooooooooooo

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