Math Is Fun Forum

ninjaman

Member

Registered: 2013-10-15

Posts: 61

partial fractions

hello

I have 4x-15 / (x+3)(x+2)

I ended up with -27 for the first one which is A, though I think A is -A because the answer for that bracket is

when x=-3 (-3+2) = -1A, so, -27 = -A. do the minus's cancel leaving only 27? I always get confused with the minus's. is there somewhere with the rules for minus written down so I can memorise them?

and -23 for the second one which is B

any help would be greatly appreciated!!!

many thanks, hope your all well!!!

simon

and remember only two months left to Christmas!!!!

Bob

Administrator

Registered: 2010-06-20

Posts: 10,629

Re: partial fractions

hi Simon,

Those values look ok to me.  Another way to check would be to substitute another value, eg x = 0, and check that both the question and answer come to the same.

question with x = 0

-15/(3x2) = -15/6

your answer with x = 0

27/3 - 23/2 = (54 - 69)/6 = -15/6

You can find some teaching materials and practice questions on positives and negatives at

http://www.mathsisfun.com/positive-nega … egers.html

and

http://www.mathsisfun.com/multiplying-negatives.html

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob