Calculus Examples

$\sum_{j = 3}^{5} \frac{1}{j^{2} - 3}$

Step 1

Expand the series for each value of $j$ .

$\frac{1}{3^{2} - 3} + \frac{1}{4^{2} - 3} + \frac{1}{5^{2} - 3}$

Step 2

Simplify.

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Step 2.1

Find the common denominator.

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Step 2.1.1

Multiply $\frac{1}{3^{2} - 3}$ by $\frac{(4^{2} - 3) (5^{2} - 3)}{(4^{2} - 3) (5^{2} - 3)}$ .

$\frac{1}{3^{2} - 3} \cdot \frac{(4^{2} - 3) (5^{2} - 3)}{(4^{2} - 3) (5^{2} - 3)} + \frac{1}{4^{2} - 3} + \frac{1}{5^{2} - 3}$

Step 2.1.2

Multiply $\frac{1}{3^{2} - 3}$ by $\frac{(4^{2} - 3) (5^{2} - 3)}{(4^{2} - 3) (5^{2} - 3)}$ .

$\frac{(4^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) ((4^{2} - 3) (5^{2} - 3))} + \frac{1}{4^{2} - 3} + \frac{1}{5^{2} - 3}$

Step 2.1.3

Multiply $\frac{1}{4^{2} - 3}$ by $\frac{(3^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) (5^{2} - 3)}$ .

$\frac{(4^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) ((4^{2} - 3) (5^{2} - 3))} + \frac{1}{4^{2} - 3} \cdot \frac{(3^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) (5^{2} - 3)} + \frac{1}{5^{2} - 3}$

Step 2.1.4

Multiply $\frac{1}{4^{2} - 3}$ by $\frac{(3^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) (5^{2} - 3)}$ .

$\frac{(4^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) ((4^{2} - 3) (5^{2} - 3))} + \frac{(3^{2} - 3) (5^{2} - 3)}{(4^{2} - 3) ((3^{2} - 3) (5^{2} - 3))} + \frac{1}{5^{2} - 3}$

Step 2.1.5

Multiply $\frac{1}{5^{2} - 3}$ by $\frac{(3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3)}$ .

$\frac{(4^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) ((4^{2} - 3) (5^{2} - 3))} + \frac{(3^{2} - 3) (5^{2} - 3)}{(4^{2} - 3) ((3^{2} - 3) (5^{2} - 3))} + \frac{1}{5^{2} - 3} \cdot \frac{(3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3)}$

Step 2.1.6

Multiply $\frac{1}{5^{2} - 3}$ by $\frac{(3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3)}$ .

$\frac{(4^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) ((4^{2} - 3) (5^{2} - 3))} + \frac{(3^{2} - 3) (5^{2} - 3)}{(4^{2} - 3) ((3^{2} - 3) (5^{2} - 3))} + \frac{(3^{2} - 3) (4^{2} - 3)}{(5^{2} - 3) ((3^{2} - 3) (4^{2} - 3))}$

Step 2.1.7

Reorder the factors of $(3^{2} - 3) ((4^{2} - 3) (5^{2} - 3))$ .

$\frac{(4^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)} + \frac{(3^{2} - 3) (5^{2} - 3)}{(4^{2} - 3) ((3^{2} - 3) (5^{2} - 3))} + \frac{(3^{2} - 3) (4^{2} - 3)}{(5^{2} - 3) ((3^{2} - 3) (4^{2} - 3))}$

Step 2.1.8

Reorder the factors of $(4^{2} - 3) ((3^{2} - 3) (5^{2} - 3))$ .

$\frac{(4^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)} + \frac{(3^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)} + \frac{(3^{2} - 3) (4^{2} - 3)}{(5^{2} - 3) ((3^{2} - 3) (4^{2} - 3))}$

Step 2.1.9

Reorder the factors of $(5^{2} - 3) ((3^{2} - 3) (4^{2} - 3))$ .

$\frac{(4^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)} + \frac{(3^{2} - 3) (5^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)} + \frac{(3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.2

Combine the numerators over the common denominator.

$\frac{(4^{2} - 3) (5^{2} - 3) + (3^{2} - 3) (5^{2} - 3) + (3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3

Simplify each term.

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Step 2.3.1

Raise $4$ to the power of $2$ .

$\frac{(16 - 3) (5^{2} - 3) + (3^{2} - 3) (5^{2} - 3) + (3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.2

Subtract $3$ from $16$ .

$\frac{13 (5^{2} - 3) + (3^{2} - 3) (5^{2} - 3) + (3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.3

Raise $5$ to the power of $2$ .

$\frac{13 (25 - 3) + (3^{2} - 3) (5^{2} - 3) + (3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.4

Subtract $3$ from $25$ .

$\frac{13 \cdot 22 + (3^{2} - 3) (5^{2} - 3) + (3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.5

Multiply $13$ by $22$ .

$\frac{286 + (3^{2} - 3) (5^{2} - 3) + (3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.6

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

$\frac{286 + (9 - 3) (5^{2} - 3) + (3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.7

Subtract $3$ from $9$ .

$\frac{286 + 6 (5^{2} - 3) + (3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.8

Raise $5$ to the power of $2$ .

$\frac{286 + 6 (25 - 3) + (3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.9

Subtract $3$ from $25$ .

$\frac{286 + 6 \cdot 22 + (3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.10

Multiply $6$ by $22$ .

$\frac{286 + 132 + (3^{2} - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.11

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

$\frac{286 + 132 + (9 - 3) (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.12

Subtract $3$ from $9$ .

$\frac{286 + 132 + 6 (4^{2} - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.13

Raise $4$ to the power of $2$ .

$\frac{286 + 132 + 6 (16 - 3)}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.14

Subtract $3$ from $16$ .

$\frac{286 + 132 + 6 \cdot 13}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.3.15

Multiply $6$ by $13$ .

$\frac{286 + 132 + 78}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.4

Add $286$ and $132$ .

$\frac{418 + 78}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.5

Add $418$ and $78$ .

$\frac{496}{(3^{2} - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.6

Simplify the denominator.

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Step 2.6.1

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

$\frac{496}{(9 - 3) (4^{2} - 3) (5^{2} - 3)}$

Step 2.6.2

Subtract $3$ from $9$ .

$\frac{496}{6 (4^{2} - 3) (5^{2} - 3)}$

Step 2.6.3

Raise $4$ to the power of $2$ .

$\frac{496}{6 (16 - 3) (5^{2} - 3)}$

Step 2.6.4

Subtract $3$ from $16$ .

$\frac{496}{6 \cdot 13 (5^{2} - 3)}$

Step 2.6.5

Multiply $6$ by $13$ .

$\frac{496}{78 (5^{2} - 3)}$

Step 2.6.6

Raise $5$ to the power of $2$ .

$\frac{496}{78 (25 - 3)}$

Step 2.6.7

Subtract $3$ from $25$ .

$\frac{496}{78 \cdot 22}$

Step 2.7

Multiply $78$ by $22$ .

$\frac{496}{1716}$

Step 2.8

Cancel the common factor of $496$ and $1716$ .

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Step 2.8.1

Factor $4$ out of $496$ .

$\frac{4 (124)}{1716}$

Step 2.8.2

Cancel the common factors.

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Step 2.8.2.1

Factor $4$ out of $1716$ .

$\frac{4 \cdot 124}{4 \cdot 429}$

Step 2.8.2.2

Cancel the common factor.

$\frac{4 \cdot 124}{4 \cdot 429}$

Step 2.8.2.3

Rewrite the expression.

$\frac{124}{429}$

Step 3

The result can be shown in multiple forms.

Exact Form:

$\frac{124}{429}$

Decimal Form:

$0.\overline{289044}$