Thread: Multiplying by conjugate

4-sqrt(s)/(s-16)


s=16

i keep multiplying this by 4+sqrt(s) and keep coming up with -12/0
the book is telling me that it's -1/8... how is this...

Originally Posted by NotEinstein

4-sqrt(s)/(s-16)


s=16

i keep multiplying this by 4+sqrt(s) and keep coming up with -12/0
the book is telling me that it's -1/8... how is this...

Did you factorise the numerator ?

Originally Posted by Moo

Did you factorise the numerator ?

I'm all jumbled right now.. now i'm getting 0/0... *cries*

Please show your steps and then we can help you locate your mistake.

0/0...

I fixed your Latex code. Take a look so you know how to write fractions now

Oh no! You changed it back to wrong.... sigh. When writing fractions in Latex, use \frac{numerator}{denominator}

I spotted your error. You don't need to plug in s=16 and get 0 in the numerator. 16-s and s-16 are only a negative sign factored out away from equal.

.

Now the 16-s cancels and you are left with

Ok I fixed your latex

Originally Posted by Jameson

I fixed your Latex code. Take a look so you know how to write fractions now

Oh no! You changed it back to wrong.... sigh. When writing fractions in Latex, use \frac{numerator}{denominator}

I spotted your error. You don't need to plug in s=16 and get 0 in the numerator. 16-s and s-16 are only a negative sign factored out away from equal.

.

Now the 16-s cancels and you are left with

so you can just do that? just toss in a negative like that? geeezz... no algebra for 5 years really messes with my head

I wouldn't call it "tossing in a negative".

Here, think about it. Let's say you have (a-b). Now if you factor out a -1 from both terms, what do you get? -1(-a+b) or -1(b-a) or -(b-a). If you distribute the -1 back through both terms you get your original sum.