Sequence Differs !

Algebra Level 1

What comes Next ?

-10, -7, -2, 5, 14, ?

21 25 27 33

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4 solutions

Nihar Mahajan
Dec 25, 2014

-10 = -10 +0

-7 = -10 + 3

-2 = -10 + 3 + 5

5 = -10 + 3 + 5 + 7

14 = -10 + 3 + 5 + 7 + 9

so , next term = -10 + 3 + 5 + 7 + 9 + 11 = 25 :)

Jack Rawlin
Dec 24, 2014

The difference between the terms increases by 2 2 every time starting at 1 1 when k = 0 k = 0 so that means that

a k = a k 1 + 2 k 1 a_k = a_{k - 1} + 2k - 1

We're looking for the value when k = 6 k = 6 so lets put that into our formula

a 6 = a 6 1 + 2 ( 6 ) 1 a_6 = a_{6 - 1} + 2(6) - 1

Since a 6 1 = a 5 a_{6 - 1} = a_5 and we know that a 5 = 14 a_5 = 14 from the question we can substitute to get

a 6 = 14 + 12 1 a_6 = 14 + 12 - 1

Which means that

a 6 = 25 a_6 = 25

Young Champ
Dec 13, 2014

Let the number be x

-7-(-10)=-7+10=3

-2-(-7)=-2+7=5

5-(-2)=5+2=7

14-5=9

Therefore,

x-14=11

=> x=25

Akshat Rahurkar
Dec 9, 2014

as we take diff. between 2 terms like, diff of 2rd term and 1nd term... ans=3 btw 3&2 ans=5 btw 4&3 ans=7 btw5&4 ans=9 conclusion the answers are in AP with comm. diff 2 therefore next term will me 14+11=25

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