# Just need a little help to figure out x in this log question

• Oct 13th 2012, 12:44 PM
M670
Just need a little help to figure out x in this log question
Find the largest value of http://webwork.mathstat.concordia.ca...dd0b8b8e91.png that satisfies: I have rewritten it like this log2(x^2/(x+1))=4 which in exponent form is 2^4=(x^2/(x+1)) so 16=(x^2/(x+1))
but I am still rusty need some direction
• Oct 13th 2012, 12:53 PM
Plato
Re: Just need a little help to figure out x in this log question
Quote:

Originally Posted by M670
Find the largest value of http://webwork.mathstat.concordia.ca...dd0b8b8e91.png that satisfies: I have rewritten it like this log2(x^2/(x+1))=4 which in exponent form is 2^4=(x^2/(x+1)) so 16=(x^2/(x+1))

Keep going: $\displaystyle x^2-16x-16=0$
• Oct 13th 2012, 01:06 PM
M670
Re: Just need a little help to figure out x in this log question
Quote:

Originally Posted by Plato
Keep going: $\displaystyle x^2-16x-16=0$

Ok form here I am sure I can do it, but can elaborate which rules you applied to get to that point
• Oct 13th 2012, 01:29 PM
skeeter
Re: Just need a little help to figure out x in this log question
$\displaystyle \frac{x^2}{x+1} = 16$

multiply both sides by $\displaystyle (x+1)$ ...

$\displaystyle x^2 = 16(x+1)$

distribute the right side and collect all terms on the left side to set the quadratic equation = 0

remember when you finish finding solutions for $\displaystyle x$, $\displaystyle x+1 > 0$