Find the 6th Term 1 , 2 , 5 , 10 , 17

$1$ , $2$ , $5$ , $10$ , $17$

Step 1

Find the first level differences by finding the differences between consecutive terms.

$1, 3, 5, 7$

Step 2

Find the second level difference by finding the differences between the first level differences. Because the second level difference is constant, the sequence is quadratic and given by $a_{n} = a n^{2} + b n + c$ .

$2$

Step 3

Solve for $a$ by setting $2 a$ equal to the constant second level difference $2$ .

Set $2 a$ equal to the constant second level difference $2$ .

$2 a = 2$

Divide each term in $2 a = 2$ by $2$ and simplify.

Divide each term in $2 a = 2$ by $2$ .

$\frac{2 a}{2} = \frac{2}{2}$

Simplify the left side.

Cancel the common factor of $2$ .

Cancel the common factor.

$\frac{2 a}{2} = \frac{2}{2}$

Divide $a$ by $1$ .

$a = \frac{2}{2}$

Simplify the right side.

Divide $2$ by $2$ .

$a = 1$

Step 4

Solve for $b$ by setting $3 a + b$ equal to the first first level difference $1$ .

Set $3 a + b$ equal to the first first level difference $1$ .

$3 a + b = 1$

Substitute $1$ for $a$ .

$3 \cdot 1 + b = 1$

Multiply $3$ by $1$ .

$3 + b = 1$

Move all terms not containing $b$ to the right side of the equation.

Subtract $3$ from both sides of the equation.

$b = 1 - 3$

Subtract $3$ from $1$ .

$b = - 2$

Step 5

Solve for $c$ by setting $a + b + c$ equal to the first term in the sequence $1$ .

Set $a + b + c$ equal to the first term in the sequence $1$ .

$a + b + c = 1$

Substitute $1$ for $a$ and $- 2$ for $b$ .

$1 - 2 + c = 1$

Subtract $2$ from $1$ .

$- 1 + c = 1$

Move all terms not containing $c$ to the right side of the equation.

Add $1$ to both sides of the equation.

$c = 1 + 1$

Add $1$ and $1$ .

$c = 2$

Step 6

Substitute the values of $a$ , $b$ , and $c$ into the quadratic sequence formula $a_{n} = a n^{2} + b n + c$ .

$a_{n} = 1 n^{2} - 2 n + 2$

Step 7

Multiply $n^{2}$ by $1$ .

$a_{n} = n^{2} - 2 n + 2$

Step 8

Substitute in the value of $n$ to find the $n$ th term.

$a_{6} = {(6)}^{2} - 2 \cdot 6 + 2$

Step 9

Simplify each term.

Raise $6$ to the power of $2$ .

$a_{6} = 36 - 2 \cdot 6 + 2$

Multiply $- 2$ by $6$ .

$a_{6} = 36 - 12 + 2$

Step 10

Simplify by adding and subtracting.

Subtract $12$ from $36$ .

$a_{6} = 24 + 2$

Add $24$ and $2$ .

$a_{6} = 26$

Find the 6th Term 1 , 2 , 5 , 10 , 17

Related Questions

Support LCMGCF.com by disabling your adblocker.