# rational expressions

• Sep 21st 2013, 09:23 AM
Bonganitedd
rational expressions
f(x) =square root of x - 1/x + 2
Determine values of x for which
1) f(x)= 0
2) f(x) will be a real number.
• Sep 21st 2013, 09:31 AM
Plato
Re: rational expressions
Quote:

Originally Posted by Bonganitedd
f(x) =square root of x - 1/x + 2
Determine values of x for which
1) f(x)= 0
2) f(x) will be a real number.

You must learn to post readable questions.

Is it it $\sqrt{\frac{x-1}{x+2}}\text{ or }\frac{\sqrt{x-1}}{x+2}$ or something else altogether?

Learn to use grouping symbols.
• Sep 21st 2013, 09:48 AM
Bonganitedd
Re: rational expressions
The first one.
• Sep 21st 2013, 09:56 AM
Plato
Re: rational expressions
Quote:

Originally Posted by Bonganitedd
The first one.

In that case you should have posted "f(x) =square root{(x - 1)/(x + 2)}"
See the grouping?

Solve $\frac{x-1}{x+2}\ge 0$.
• Sep 21st 2013, 10:19 AM
Bonganitedd
Re: rational expressions
X>=1 nt sure abt the denomenator
• Sep 21st 2013, 10:33 AM
HallsofIvy
Re: rational expressions
Do you know "if a> b and c is positive then ac> bc. If a> b and c is negative then ac< bc."

If x+ 2 is positive, then multiplying both sides by it gives $x- 1\ge 0$. When is x+ 2 positive?

If x+2 is negative, then multiplying both sides by it gives $x- 1\le 0$. When is x+ 2 negative?
• Sep 21st 2013, 12:41 PM
votan
Re: rational expressions
• Sep 24th 2013, 10:44 AM
Bonganitedd
Re: rational expressions
Thanks you all who contributed.
I now understand the problem
1) The expression will be equal to zero if we set the radicand numerator = 0
2)f(x) will be real 1) x is nt = -2
X>=1 or x< -2
• Sep 24th 2013, 02:10 PM
HallsofIvy
Re: rational expressions
Do you now understand that this was NOT a "rational expression"?