Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**Winatte****Member**- Registered: 2022-12-29
- Posts: 1

Hi folks, after researching and studying for the past 2 days on this, I am still unable to find a single darn answer! I feel pretty low because of this, so would appreciate any help you can give.

So this is my question:

Simplify the following summations to the form an3 +

bn2+cn. Give values for a, b and c for each question.

1.

2.

3.

4.

I know the answers to the first three can be built up from these:

But I have no clue actually how to get the answers, as I was only taught and shown how to use set formulas on a given sum, so for instance

would be n(n+1) over 2.I am stuck!

Even a link to a website which could help me understand this question a bit better would be much appreciated.

Offline

**Bob****Administrator**- Registered: 2010-06-20
- Posts: 9,631

hi Winatte

Welcome to the forum.

The formula for the sum of squares ( 1 + 4 + 9 + 16 + ... + n^2) is

Sum = n(n+1)(2n+1)/6

Substitute n = 1, 2, 3 etc to show that it works.

There are also similar formulas for the sum of cubes and higher powers but they get increasingly complicated.

Q1 is just 5 + 5 + 5 + 5 ... 'n' times = 5n. I don't understand what " an3 + bn2 + cn" means for this.

We can make more progress with this over several posts so please reply.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob

Offline

Pages: **1**