Algebra Examples

$a_{n} = 21 - 2 n^{2}$

Step 1

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

$a_{3} = 21 - 2 {(3)}^{2}$

Step 2

Simplify each term.

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Step 2.1

Raise $3$ to the power of $2$ .

$a_{3} = 21 - 2 \cdot 9$

Step 2.2

Multiply $- 2$ by $9$ .

$a_{3} = 21 - 18$

Step 3

Subtract $18$ from $21$ .

$a_{3} = 3$