View Full Version : homework help

Samantha31

07-20-2009, 07:51 PM

I have been trying to work out this problem and I can't figure out what I am doing wrong. If someone could walk me through it I would appreciate the help.

5-x/4x-20

I got 5-x/4(x-5) but i'm not even sure if I'm allowed to seperate the bottom portion.

wjm11

07-20-2009, 08:34 PM

5-x/4x-20

I got 5-x/4(x-5) but i'm not even sure if I'm allowed to seperate the bottom portion.

You have started correctly. However, there is more that can be done to simplify this expression.

Consider the expression “a-b”. If we factor out a “-1”, we can rewrite it as

a-b = (-1)(b-a)

or simply

a-b = -(b-a)

Make sense? If we apply this to your problem, we can rewrite the numerator:

(5-x)/(4x-20) = (5-x)/[4(x-5)] = -(x-5)/[4(x-5)]

Now we have common factors in both the numerator and denominator, and they can be canceled.

-(x-5)/[4(x-5)] = -1/(4) = -1/4

Hope that helps.

Denis

07-20-2009, 10:31 PM

5-x/4x-20

(5 - x) / (4x - 20)

Brackets VERY important here; as is, what you typed means 5 - 20 - x/4x = 5 - 20 - 1/4 = - 15 1/4 = -61/4

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