## What is the algebraic form of the sequence 3 6 10 15?

This is the Triangular Number Sequence: 1, 3, 6, 10, 15, 21, 28, 36, 45.

## What is the sum of n terms of the following series 1 3 6 10 15 21?

The number of terms in the sequence 1, 3, 6, 10, 15, 21,……, 5050 is.

## Why is 28 a triangular number?

Triangular numbers correspond to the first-degree case of Faulhaber’s formula. Alternating triangular numbers (1, 6, 15, 28.) are also hexagonal numbers. where Mp is a Mersenne prime. No odd perfect numbers are known; hence, all known perfect numbers are triangular.

## Is 13 a happy number?

The first few happy numbers are 1, 7, 10, 13, 19, 23, 28, 31, 32, 44, 49, 68, 70, 79, 82, 86, 91, 94, 97, 100. (OEIS A007770).

## Is 13 a Fibonacci number?

The Fibonacci Sequence is the series of numbers: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34.

## Why is 9 a sad number?

number symbolism In contrast to 8, the number 9 often represents pain or sadness. The 16th-century Catholic theologian Peter Bungus pointed out that the Ninth Psalm predicts the coming of the Antichrist.

## What is a sad number?

The numbers for which the process of summing up of the squares of its digits ends in 1 are happy numbers. On the other hand, numbers that don’t end in 1 are called unhappy or sad numbers. Here, the number 36 loops endlessly in a cycle which doesn’t end in 1. Therefore 36 is an unhappy or sad number.

## How do you solve an algebraic expression with two variables?

In a two-variable problem rewrite the equations so that when the equations are added, one of the variables is eliminated, and then solve for the remaining variable. Step 1: Multiply equation (1) by -5 and add it to equation (2) to form equation (3) with just one variable.

## How do you solve for three variables?

Here, in step format, is how to solve a system with three equations and three variables:

1. Pick any two pairs of equations from the system.
2. Eliminate the same variable from each pair using the Addition/Subtraction method.
3. Solve the system of the two new equations using the Addition/Subtraction method.