Limits problem , i cant solve

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November 7th 2009, 07:18 PM
student0451

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Limits problem , i cant solve

Hey everyone again,

I am having trouble with certain limit problems on my exam revision maths booklet , I have attached the questions and answers.

I assume the steps involved to solve questions 6(b), 8(b), 10(a) are as followed: These questions

step 1: Sub in the limits
step 2: if it equals (0/0) we must factorise
step 3: sub final values of factorise.

I cant get the answer. I think it is basic operations I cant do but I am not entirely sure. Please correct me , where I am wrong.
November 7th 2009, 08:52 PM
mr fantastic

Quote:

Originally Posted by student0451

Hey everyone again,

I am having trouble with certain limit problems on my exam revision maths booklet , I have attached the questions and answers.

I assume the steps involved to solve questions 6(b), 8(b), 10(a) are as followed: These questions

step 1: Sub in the limits
step 2: if it equals (0/0) we must factorise
step 3: sub final values of factorise.

I cant get the answer. I think it is basic operations I cant do but I am not entirely sure. Please correct me , where I am wrong.

I assume 6(b), 8(b) and 10(a) are the ones you want help with?

Please type out each question and show what you've been able to do and say where you get stuck.
November 7th 2009, 09:23 PM
student0451

2 Attachment(s)

hey fantastic,

Here is what i have done,

Question 6

I have sub it in , i get (0/0) , I need to factorise but i cant find the factors.

Question 7

(-18/-18)

I dont know exactly what to do after this step.

question 10

I simplify then factorize then sub it in
November 7th 2009, 09:51 PM
mr fantastic

Quote:

Originally Posted by student0451

hey fantastic,

Here is what i have done,

Question 6

I have sub it in , i get (0/0) , I need to factorise but i cant find the factors.

Question 7

(-18/-18)

I dont know exactly what to do after this step.

question 10

I simplify then factorize then sub it in

Please type out the questions, as requested earlier. I don't like having to click on things to see them properly and then having to switch back and forth between my reply and what I'm looking at.
November 7th 2009, 09:58 PM
mr fantastic

Quote:

Originally Posted by mr fantastic

Please type out the questions, as requested earlier. I don't like having to click on things to see them properly and then having to switch back and forth between my reply and what I'm looking at.

The work you have shown is wrong. eg. When x = -3, x^2 does not equal -9. It equals (-3)^2 = 9. And 4^2 = 16 not 17.

Note:

$\frac{2x^2 - 3x - 20}{x - 4} = \frac{(2x + 5)(x - 4)}{x - 4} = 2x + 5$ provided $x \neq 4$ .

$\frac{x^2 + 8x + 15}{x^2 - x - 12} = \frac{(x+3)(x + 5)}{(x + 3)(x - 4)} = \frac{x + 5}{x - 4}$ provided $x \neq -3$ .

And you urgently need to review how to factorise since you're obviously expected to be able to.
November 7th 2009, 09:59 PM
student0451

I am sorry Fantastic, do I use the ladex editor? because I am relative new to this website.
November 7th 2009, 10:02 PM
student0451

well thank you,

I definitely need to learn this skill better.