# function: f(x) = 2 + 3 / x - 4 / x + 1 find x when f(x) = 2

#### ptebwwong

##### New member
I need help with this problem.

f(x)= 2 + 3
_____ ______
x-4 x+1

Find x when f(x)=2.

I plugged in the numbers & got -3/2.5 so x=-1.2.

Is this correct.

#### arthur ohlsten

##### Full Member
Re: function help

I believe you mode a error, but my math could be wrong. Please check my algebra

f[x]= 2/[x-4] + 3 / [x+1]
find x when f[x]=2

2= 2/[x-4] + 3/[x+1]
place over common denominator [x-4][x+1]
2= {2[x+1]+3[x-4] }/[x-4][x+1]
2[x-4][x+1]= 2x+2+3x-12
2[x^2-3x-4]= 5x-10
2x^2-6x-8=5x-10
2x^2-11x +2=0
x=11+/-[121-16]^1/2 all over 4
x=11+/- 10.25 all over 4
x= 21.25/4
x=.75/4

x=5.31 or x= .19

#### mmm4444bot

##### Super Moderator
Staff member
arthur ohlsten said:
... Please check my algebra ... There are some missing grouping symbols, Arthur; otherwise, it looks good.

2 = 2/[x - 4] + 3/[x + 1]

place over common denominator [x - 4][x + 1]

2 = {2[x + 1] + 3[x - 4]}/{[x - 4][x + 1]}

2[x - 4][x + 1] = 2x + 2 + 3x - 12

2[x^2 - 3x - 4] = 5x - 10

2x^2 - 6x - 8 = 5x - 10

2x^2 - 11x + 2 = 0

x = 11 +/- [121 - 16]^(1/2) all over 4

x = 11 +/- (105)^(1/2) all over 4

x = 11/4 + ?105/4

x = 11/4 - ?105/4

x ? 5.31 or x ? .19

#### arthur ohlsten

##### Full Member
Re: function help

Arthur

#### mmm4444bot

##### Super Moderator
Staff member
arthur ohlsten said:
Your algebra is correct This is an unreferenced pronoun, Arthur. Are you talking to yourself?

Arthur

#### arthur ohlsten

##### Full Member
Re: function help

mmm.....
I am afraid my degrees are in Physics, Math, and Engineering, not in English.