# finding a and b (question must be completed by 11 o'clock tonight!!)

• Oct 1st 2009, 05:09 PM
chris097
finding a and b (question must be completed by 11 o'clock tonight!!)
f(x)= (x^2 - 1) / (x - 1) if x<1
= ax^2 - bx + 1 if 1 <= x < 3
= 4x - a + b if x => 3

find a and b

all i know so far is that you must use a limit as x approaches 1 in the first equation to get 2

then where should i go?

thank you for your help :)
• Oct 1st 2009, 05:18 PM
pickslides

$\displaystyle f(x)= \frac{x^2 - 1}{x - 1}= \frac{(x - 1)(x+1)}{x - 1} = x + 1 , x\neq 1$
• Oct 1st 2009, 05:23 PM
chris097
http://i38.tinypic.com/rus96s.gif

sorry
this is what the question is

find a and b
• Oct 1st 2009, 11:28 PM
mr fantastic
Quote:

Originally Posted by chris097
http://i38.tinypic.com/rus96s.gif

sorry
this is what the question is

find a and b

I suppose we're meant to assume that the question said something like "Find the values of a and b so that f(x) is continuous for all values of x" ....? Solve the following two equations simulataneously (I suggest you simplify them first):

1 + 1 = a - b + 1

a(3)^2 - b(3) + 1 = 4(3) - a + b

And since your deadline suggests that this is assignment that in all likelihood counts towards you final grade and is therefore meant to be your own work, the thread is now closed.