Number pattern Question... O lvl
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4,7,12,19,28,39
Find the nth term...
I once got this correct last time but i tried doing this today again but i cant find the answer -.-" -
from 4,Originally posted by popikachu:4,7,12,19,28,39
Find the nth term...
I once got this correct last time but i tried doing this today again but i cant find the answer -.-"
+3 +5 +7 +9 +11
What I will do is change it to
3 +1 +3 +5 +7 +9 +11
note that the right side is like a AP, first term = 1, difference = 2
hence, summation of AP is n/2 (2a + (n-1)d)
Ans that you should get is:
3 + n/2 (2 + 2n - 2)
final answer: 3 + n^2
But hor, APGP is not in O level syllabus, and you don't need to do it this way. I just want to play
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Nth term=a+(n-1)d
*paiseh, only works for a stable increment... -
should beOriginally posted by popikachu:4,7,12,19,28,39
Find the nth term...
I once got this correct last time but i tried doing this today again but i cant find the answer -.-"
3 + summation i=0 -> n-1 (2n+1)
should be bah -
why so jialat one
3 + n^2 is the answer mah
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work backwards you are right.Originally posted by eagle:from 4,
+3 +5 +7 +9 +11
What I will do is change it to
3 +1 +3 +5 +7 +9 +11
note that the right side is like a AP, first term = 1, difference = 2
hence, summation of AP is n/2 (2a + (n-1)d)
Ans that you should get is:
3 + n/2 (2 + 2n - 2)
final answer: 3 + n^2
But hor, APGP is not in O level syllabus, and you don't need to do it this way. I just want to play
but how you derive at the solution ?
i was thinking that the +3+5+7+9 thingy was 2n+1, but stuck there liao
and wad is ap -
haiz...Originally posted by eagle:from 4,
+3 +5 +7 +9 +11
What I will do is change it to
3 +1 +3 +5 +7 +9 +11
note that the right side is like a AP, first term = 1, difference = 2
hence, summation of AP is n/2 (2a + (n-1)d)
Ans that you should get is:
3 + n/2 (2 + 2n - 2)
final answer: 3 + n^2
But hor, APGP is not in O level syllabus, and you don't need to do it this way. I just want to play
so easy de thing i make until so complecated...
i got
(n+1) then must time dunno what what what until i luan then stuck... and using 2s x something to solve it... lol... -
AP is arithmetic progressionOriginally posted by spadeTwo:work backwards you are right.
but how you derive at the solution ?
i was thinking that the +3+5+7+9 thingy was 2n+1, but stuck there liao
and wad is ap
During my time, it was in A maths syllabus, that's why all these number patterns can do. Now out of syllabus liao, only in A level syllabus -
actually if got the 'magic' eye, you can always minus 3 to all terms and show that the remaining terms are perfect squaresOriginally posted by popikachu:haiz...
so easy de thing i make until so complecated...
i got
(n+1) then must time dunno what what what until i luan then stuck... and using 2s x something to solve it... lol... -
now teach us how to solve without using a mathsOriginally posted by eagle:AP is arithmetic progression
During my time, it was in A maths syllabus, that's why all these number patterns can do. Now out of syllabus liao, only in A level syllabus -
I posted a formula above...Originally posted by spadeTwo:now teach us how to solve without using a maths -
i dont really understand leh .Originally posted by wonderamazement:I posted a formula above... -
you must have the experience that forOriginally posted by spadeTwo:now teach us how to solve without using a maths
1 4 9 16 25 36 49 64
the difference is
3 5 7 9 11 13 15..........
then when u see similar questions, you know liao -
ginger still is old 1 hot.Originally posted by eagle:you must have the experience that for
1 4 9 16 25 36 49 64
the difference is
3 5 7 9 11 13 15..........
then when u see similar questions, you know liao -
pika good lor.. go find other ppl..
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you one so troublesome must remember formula some more. just use the summation symbol can le. they ask for the n value only mahOriginally posted by eagle:why so jialat one
3 + n^2 is the answer mah -
a=first numberOriginally posted by spadeTwo:i dont really understand leh .
d=difference
so this can only be applied to a standard increment per number... -
I always hate number patterns
Either very easy, or cannot solve -
number pattern if appear in first few qns, i will welli happy
if appear on LAST qn, GG for me, i will skip (but dunno to wad qn) -
N^2 +3...i stare at the thing for 10 seconds bingo
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if u use the summation symbol in your answer, I'm pretty sure they will not give full marks. Why should they bother to confirm it if the Cambridge answer sheet did not use the summation sign?Originally posted by hisoka:you one so troublesome must remember formula some more. just use the summation symbol can le. they ask for the n value only mah
Another way, if you can see it, and using building on your way is
3 + SUM (2i-1) from i = 1 to i = n
SUM(-1) from i=1 to i=n = -n
SUM(2i) from i=1 to i=n = n(n+1)
so you get 3 + n^2 + n - n = 3 + n^2 -
Use APGP la.
Dont say dun know
if dun know go learn! -
or remember this rules:
Sum (i) from i=1 to i=n = n(n+1)/2
Sum (i^2) from i=1 to i=n = n(n+1)(2n+1)/6
Sum (i^3) from i=1 to i=n = ( n(n+1)/2 )^2
if i does not start from 1, you can always make it start from 1