# Limits problem , i cant solve

• Nov 7th 2009, 07:18 PM
student0451
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.
• Nov 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.
• Nov 7th 2009, 09:23 PM
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
• Nov 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.
• Nov 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.
• Nov 7th 2009, 09:59 PM
student0451
I am sorry Fantastic, do I use the ladex editor? because I am relative new to this website.
• Nov 7th 2009, 10:02 PM
student0451
well thank you,

I definitely need to learn this skill better.