# Maths

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#1
If Ur=1/6r(r+1)(4r+11)

Ur-Ur-1=r(2r+3)
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2 years ago
#2
(Original post by Jjjj112)
If Ur=1/6r(r+1)(4r+11)

Ur-Ur-1=r(2r+3)
What is the question, what have you tried?
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#3
I tried but I don’t know the answer and thts the question
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2 years ago
#4
(Original post by Jjjj112)
I tried but I don’t know the answer and thts the question
I'm presuming that there's a bit more text in the question and you have to "show that .." or

So given Ur=1/6r(r+1)(4r+11)
what is
Ur-1 = ...
(just substitute "r-1" in place of "r") and what is it when you subtract them?
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#5
I tried that
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2 years ago
#6
(Original post by Jjjj112)
I tried that
So what did you get for Ur-1?
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2 years ago
#7
Substitute r-1 in place of r to find U(r-1) then subtract this from U(r) then factorise it and simplify
Last edited by Tgm11801; 2 years ago
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2 years ago
#8
(Original post by Tgm11801)
I assume this is what is needed
Could you pls edit your post, the aim is to get the OP to work though the question, rather than just giving the answer.
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#9
Could u plz work it out and see if u get the given answer
1
2 years ago
#10
I do get the given answer, it is correct
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#11
Could u show me the working out
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2 years ago
#12
Attempt the problem yourself. Show me your attempt at substituting and simplifying the function at r-1
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#13
It’s fine now I understand
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2 years ago
#14
Good
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#15
Thank you
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#16
(Original post by Tgm11801)
Good
Could u explain domain and range how u would work it out?
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2 years ago
#17
The domain is the values that a function can take, can be put in the input. For example for the natural log only positive numbers are in the domain. The range is the values that can be outputs of the function, so for x^2 all positive y values
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#18
Sorry thts rlly confusing
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2 years ago
#19
So on a graph the domain is the x values on the x axis that are allowed, and the range is the y values that can happen. So for y=x^2 the range is y isnt negative because nothing squared is negative. For the graph y=1/x the domain is all x that isnt 0 because you cant divide by zero, its all about what is allowed to be put into the function
1
2 years ago
#20
is this gcse or a level
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