The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

Maths help asap

Simplify into a single factorised expression.
(x – 3)^2 + 5(x – 3)^3

and
4x(2x + 1)^3 + 5(2x + 1)^4

Scroll to see replies

Original post by BenHarrow
Simplify into a single factorised expression.
(x – 3)^2 + 5(x – 3)^3

and
4x(2x + 1)^3 + 5(2x + 1)^4


You can factorise out the (x-3)^2 in the first one.

Post your workings and what you've tried.
Original post by BenHarrow
Simplify into a single factorised expression.
(x – 3)^2 + 5(x – 3)^3

and
4x(2x + 1)^3 + 5(2x + 1)^4


the first one, factorise (x+3)^2 out and the second one factorise (2x+1)^3 oit
Reply 3
Avatar for BenHarrow
BenHarrow
OP
2
Original post by brainmaster
the first one, factorise (x+3)^2 out and the second one factorise (2x+1)^3 oit

THanks man but the thing i am confused about is how you factorise that out as the answer for the first one is (x – 3)^2(5x – 14) but if you factorise (x-3)^2 surely it will be gone from equation, i just dont know how to factorise that step by step
Original post by BenHarrow
THanks man but the thing i am confused about is how you factorise that out as the answer for the first one is (x – 3)^2(5x – 14) but if you factorise (x-3)^2 surely it will be gone from equation, i just dont know how to factorise that step by step

Factorise does not mean remove it completely.

(x - 3)^2 {......... + ........)
Reply 5
Avatar for BenHarrow
BenHarrow
OP
2
Original post by Muttley79
Factorise does not mean remove it completely.

(x - 3)^2 {......... + ........)

how does it work then i know how to factorise normally but i dont understand this
Original post by BenHarrow
THanks man but the thing i am confused about is how you factorise that out as the answer for the first one is (x – 3)^2(5x – 14) but if you factorise (x-3)^2 surely it will be gone from equation, i just dont know how to factorise that step by step


(x-3)^2(1 5(x-3))
does it make sense now?
(edited 4 years ago)
Original post by Muttley79
Factorise does not mean remove it completely.

(x - 3)^2 {......... + ........)


a simple way to understand this is to let (x-3) = y
so you have y^2+5y^3
y^2(1+5y)
Original post by brainmaster


does it make sense now?

It is against the rules to post a solution - please edit.
Reply 9
Avatar for BenHarrow
BenHarrow
OP
2
Original post by brainmaster
(x-3)^2(1+5(x-3))
(x-3)^2(1+5x-15)
(x-3)^2(5x-14)

does it make sense now?

can you do second one so i can fully understand as i am confused as to how the 1 just moves into the brackets
Original post by Muttley79
It is against the rules to post a solution - please edit.


sorry for that. is it fine now?
Reply 11
Avatar for BenHarrow
BenHarrow
OP
2
Original post by brainmaster
a simple way to understand this is to let (x-3) = y
so you have y^2+5y^3
y^2(1+5y)

I understand that yes but i just dont understand how its the same for this equation
Original post by BenHarrow
how does it work then i know how to factorise normally but i dont understand this

(x – 3)^2 + 5(x – 3)^3= (x - 3)^2 [ what do you need here to multiply to get the first term + what do you need to get the second term]
Original post by brainmaster
sorry for that. is it fine now?

I think you've lost a sign but please don't do the second one for the OP.
Original post by BenHarrow
I understand that yes but i just dont understand how its the same for this equation


try this, let y=(x-3) and then factorise the equation fully and they replace y=x-3 back and see what you get. the substitute makes it simpler to see and understand
Original post by Muttley79
I think you've lost a sign but please don't do the second one for the OP.


won't do it
Original post by BenHarrow
can you do second one so i can fully understand as i am confused as to how the 1 just moves into the brackets

No, you need to try it for yourself. The '1' is what you need in the bracket to get the original term when it is multiplied out again.

SImpler example: Factorise x^2 + x

x^2 + x = x( x + 1) x is a common factor here so I've taken it outside the bracket then inside the bracket I need an 'x' to get the x^2 and a '+1' to get the x.
Reply 17
Avatar for BenHarrow
BenHarrow
OP
2
Original post by Muttley79
No, you need to try it for yourself. The '1' is what you need in the bracket to get the original term when it is multiplied out again.

SImpler example: Factorise x^2 + x

x^2 + x = x( x + 1) x is a common factor here so I've taken it outside the bracket then inside the bracket I need an 'x' to get the x^2 and a '+1' to get the x.

Oh ok i understand that thanks both of you for the help i will try secomd example now
Original post by BenHarrow
Oh ok i understand that thanks both of you for the help i will try secomd example now

Post your working and we can help :smile:
Reply 19
Avatar for BenHarrow
BenHarrow
OP
2
I got right answer through method thanks, final question i have is this

simplify the following

(2πh^2/rb)/4/3πhr^2

i have some current working but struggling to get to answer

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you