Saturday

August 2, 2014

August 2, 2014

Posted by **qwerty** on Thursday, November 20, 2008 at 10:58pm.

it describes the number of total cards of a cardhouse as each bottom layer is added

help

- math/algebra -
**Reiny**, Friday, November 21, 2008 at 7:42amI don't know what method you use, but I noticed that the second differences for the data is a constant 3, as you noted.

That tells us that the data can be expressed by a quadratic function

let the function by y = ax^2 + bx + c

and sub in (1,2),(2,7), and (3,15), the first 3 given values.

this gives you 3 equations in 3 unknowns which solve quite nicely to

a = 3/2

b = 1/2

c = 0

so the function is y = (3/2)x^2 + x/2

or

y = (3x^2 + x)/2

test it for the last value, it works.

**Related Questions**

algebra - Could someone check my work; 1. Generate the first five terms in the ...

algebra - a student write that an=3n+1 is a explicit formula for the sequence 1,...

another question algebra - write an explicit formula for the sequence 7,2,-3,-8...

Algebra - A = - 113 and A = -213 20 40 this is an arithmetic sequence and i have...

algebra 2 - write an explicit formula for the sequence of 1/2, 3/7, 1/3, 5/19, 3...

math30 - Sequences 1)A sequence has a first term of 24 and every other term is ...

alg - write the explicit formula for the sequence 7,2,-3,-8,-13 and find a 14

algebra - Need help with this one write an explicit formula for the sequence 1/2...

algebra - Robin bought a computer for $1,250. It will depreciate, or decrease in...

math - 51.A sequence t is defined where the first term is –4. Each successive ...