indices, core 1 AS

hi, im trying to do some maths homework set by my teacher, im stuck on a completly simple problem, that i cannot see the solution for, is there any chance anyone would walk me through how to do it, but without giving me the final answer, because i am at a loss of where to start, sorry x

heres the question anyway ("^" is to the power of and "/" is divide)

simplify this expression 21a^3 b^2 / 7ab^4

thanks, ash xx

Reply 1

bottomness

the 21 and the 7 cancel out to leave three on the top (if u divide the top and bottom by 7), u can also divide the top and bottom by a, and by b^2.
u can do this because they are common in both the top and bottom of the expression
so the answer would be, i think, 3a^2/b^2
if this is not the answer in the back of the book im sorry, may have gone wrong somewhere

Reply 2

kexy

ive just seen how iu can write it out better for you to understand, sorry guys (and girls) 21a³b²÷7ab⁴

Reply 3

kexy

the answer in the back of the book is a²b-2a :s-smilie:

, like i said i bet you get allot of people coming here for quick answers but i care about my work and this has got me stumped, iv go to hav emy tea, but il be back in around 20mins, thanks again

Reply 4

bottomness

are u sure u are looking at the right answers? because there is no way u can get a²b-2a from 21a³b²÷7ab4 because there is no way u can get -2a as there are no +s or -s in the starting thing, what book are u using and what question and exercise in that book, as i have one infront of me, and would make more sense

Reply 5

bottomness

found your problem, u are doing edexcel core maths 1, and u are doing question 12 in exercise 1B, however u are looking at the answer in the back of the book to question 12 in exercise 1A
i was wrong too though to be honest, u do basically the same as i said before but the b's go to b^-2 as there is b^4 on the bottom and b^2 on the top and 2-4=-2
you probably know the answer really but were just confused about the answer given, i have done that so many times myself

Reply 6

kexy

i apologise, the correct answer is 3a²b^-2 which is the same as your answer, but written in a differnt way, sorry x the book im using is heinemann modular mathmatics for edexcel as and a level, core mathmatics 1, the question is exercise 1b, 12 sorry again

Reply 7

kexy

beat me to it, yeah u were right, thsi is why i was confused, thanks anyway x

Reply 8

bottomness

seriously dont worry, i wasnt meant to sound mean before, i really wasnt, i was just confused myself

Reply 9

kexy

right, im back, :smile:

sorry for this, i m sooo out of touch, is this normal to struggle when u first start maths again after GCSEs, i seem to have forgoten so many simple things, and yet i got an A in the exams :s-smilie:

anyway, my question is this

if you had the sum whicn went along the lines of 3(x²)³
does that mean 3*x² all cubed or x², cubed * 3? :s-smilie:

cheers

Reply 10

Chewwy

porter2002

right, im back, :smile:

sorry for this, i m sooo out of touch, is this normal to struggle when u first start maths again after GCSEs, i seem to have forgoten so many simple things, and yet i got an A in the exams :s-smilie: