# Exponents on polynomials

• May 22nd 2010, 03:26 AM
dwatkins741
Exponents on polynomials
I'm having trouble with this problem.

The only way I can get the answer the book gives is to illegally remove the exponent of 1/2 from the 1st term.

Problem: (2x+1)^(1/2) + (x+3)(2x+1)^(-1/2)

my attempt:
=(2x+1)^(1/2) + ((x+3) / ((2x + 1)^(1/2))
(I don't see any like terms here unless I remove the exponent)

Another question: I see that I should move
(2x+1)^(-1/2) to the denominator because of the negative exponent. When I do this, does it go in the denominator of all the other terms, or just in the den of (x+3)?

Please explain what I'm doing wrong. Thanks alot!!

• May 22nd 2010, 03:59 AM
pickslides
$\displaystyle (2x+1)^{\frac{1}{2}} + (x+3)(2x+1)^{\frac{-1}{2}}=(2x+1)^{\frac{1}{2}} + \frac{(x+3)}{(2x+1)^{\frac{1}{2}}}=\frac{(2x+1) +(x+3)}{(2x+1)^{\frac{1}{2}}}$

now simplify the numerator
• May 22nd 2010, 04:07 AM
tonio
Quote:

Originally Posted by dwatkins741
I'm having trouble with this problem.

The only way I can get the answer the book gives is to illegally remove the exponent of 1/2 from the 1st term.

Problem: (2x+1)^(1/2) + (x+3)(2x+1)^(-1/2)

my attempt:
=(2x+1)^(1/2) + ((x+3) / ((2x + 1)^(1/2))
(I don't see any like terms here unless I remove the exponent)

Another question: I see that I should move (2x+1)^(-1/2) to the denominator because of the negative exponent. When I do this, does it go in the denominator of all the other terms, or just in the den of (x+3)?

Please explain what I'm doing wrong. Thanks alot!!

$\displaystyle \sqrt{2x+1}+\frac{x+3}{\sqrt{2x+1}}=\frac{2x+1+x+3 }{\sqrt{2x+1}}=\frac{3x+4}{\sqrt{2x+1}}$ , via $\displaystyle \sqrt{a}+\frac{1}{\sqrt{a}}=\frac{a+1}{\sqrt{a}}$ ... common denominator and stuff.

Tonio
• May 22nd 2010, 04:53 AM
dwatkins741
That's new to me
That formula you gave, Tonio, was totally new to me. I never knew you could do that with radicals. I tested it out and it works. Thanks alot. Very helpful.
• May 22nd 2010, 06:06 AM
Prove It
Quote:

Originally Posted by dwatkins741
I'm having trouble with this problem.

The only way I can get the answer the book gives is to illegally remove the exponent of 1/2 from the 1st term.

Problem: (2x+1)^(1/2) + (x+3)(2x+1)^(-1/2)

my attempt:
=(2x+1)^(1/2) + ((x+3) / ((2x + 1)^(1/2))
(I don't see any like terms here unless I remove the exponent)

Another question: I see that I should move
(2x+1)^(-1/2) to the denominator because of the negative exponent. When I do this, does it go in the denominator of all the other terms, or just in the den of (x+3)?

Please explain what I'm doing wrong. Thanks alot!!

I expect you've been asked to simplify this... To simplify expressions involving fractions, you need a common denominator.

$\displaystyle \sqrt{2x + 1} + \frac{x + 3}{\sqrt{2x + 1}} = \frac{\sqrt{2x + 1}\sqrt{2x + 1}}{\sqrt{2x + 1}} + \frac{x + 3}{\sqrt{2x + 1}}$

$\displaystyle = \frac{2x + 1}{\sqrt{2x + 1}} + \frac{x + 3}{\sqrt{2x + 1}}$

$\displaystyle = \frac{2x + 1 + x + 3}{\sqrt{2x + 1}}$

$\displaystyle = \frac{3x + 4}{\sqrt{2x + 1}}$.

I choose to write fractions with rational denominators though, so to clean it up even more...

$\displaystyle = \frac{(3x + 4)\sqrt{2x + 1}}{2x + 1}$.