Precalculus Examples

${(7 a + b)}^{3}$

Step 1

Use the binomial expansion theorem to find each term. The binomial theorem states ${(a + b)}^{n} = \sum_{k = 0}^{n} n C k \cdot (a^{n - k} b^{k})$ .

$\sum_{k = 0}^{3} \frac{3!}{(3 - k)! k!} \cdot {(7 a)}^{3 - k} \cdot {(b)}^{k}$

Step 2

Expand the summation.

$\frac{3!}{(3 - 0)! 0!} \cdot {(7 a)}^{3 - 0} \cdot {(b)}^{0} + \frac{3!}{(3 - 1)! 1!} \cdot {(7 a)}^{3 - 1} \cdot {(b)}^{1} + \frac{3!}{(3 - 2)! 2!} \cdot {(7 a)}^{3 - 2} \cdot {(b)}^{2} + \frac{3!}{(3 - 3)! 3!} \cdot {(7 a)}^{3 - 3} \cdot {(b)}^{3}$

Step 3

Simplify the exponents for each term of the expansion.

$1 \cdot {(7 a)}^{3} \cdot {(b)}^{0} + 3 \cdot {(7 a)}^{2} \cdot {(b)}^{1} + 3 \cdot {(7 a)}^{1} \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4

Simplify each term.

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Step 4.1

Multiply ${(7 a)}^{3}$ by $1$ .

${(7 a)}^{3} \cdot {(b)}^{0} + 3 \cdot {(7 a)}^{2} \cdot {(b)}^{1} + 3 \cdot {(7 a)}^{1} \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.2

Apply the product rule to $7 a$ .

$7^{3} a^{3} \cdot {(b)}^{0} + 3 \cdot {(7 a)}^{2} \cdot {(b)}^{1} + 3 \cdot {(7 a)}^{1} \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.3

Raise $7$ to the power of $3$ .

$343 a^{3} \cdot {(b)}^{0} + 3 \cdot {(7 a)}^{2} \cdot {(b)}^{1} + 3 \cdot {(7 a)}^{1} \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.4

Anything raised to $0$ is $1$ .

$343 a^{3} \cdot 1 + 3 \cdot {(7 a)}^{2} \cdot {(b)}^{1} + 3 \cdot {(7 a)}^{1} \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.5

Multiply $343$ by $1$ .

$343 a^{3} + 3 \cdot {(7 a)}^{2} \cdot {(b)}^{1} + 3 \cdot {(7 a)}^{1} \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.6

Apply the product rule to $7 a$ .

$343 a^{3} + 3 \cdot (7^{2} a^{2}) \cdot {(b)}^{1} + 3 \cdot {(7 a)}^{1} \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.7

Raise $7$ to the power of $2$ .

$343 a^{3} + 3 \cdot (49 a^{2}) \cdot {(b)}^{1} + 3 \cdot {(7 a)}^{1} \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.8

Multiply $49$ by $3$ .

$343 a^{3} + 147 a^{2} \cdot {(b)}^{1} + 3 \cdot {(7 a)}^{1} \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.9

Simplify.

$343 a^{3} + 147 a^{2} \cdot b + 3 \cdot {(7 a)}^{1} \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.10

Simplify.

$343 a^{3} + 147 a^{2} b + 3 \cdot (7 a) \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.11

Multiply $7$ by $3$ .

$343 a^{3} + 147 a^{2} b + 21 a \cdot {(b)}^{2} + 1 \cdot {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.12

Multiply ${(7 a)}^{0}$ by $1$ .

$343 a^{3} + 147 a^{2} b + 21 a b^{2} + {(7 a)}^{0} \cdot {(b)}^{3}$

Step 4.13

Apply the product rule to $7 a$ .

$343 a^{3} + 147 a^{2} b + 21 a b^{2} + 7^{0} a^{0} \cdot {(b)}^{3}$

Step 4.14

Anything raised to $0$ is $1$ .

$343 a^{3} + 147 a^{2} b + 21 a b^{2} + 1 a^{0} \cdot {(b)}^{3}$

Step 4.15

Multiply $a^{0}$ by $1$ .

$343 a^{3} + 147 a^{2} b + 21 a b^{2} + a^{0} \cdot {(b)}^{3}$

Step 4.16

Anything raised to $0$ is $1$ .

$343 a^{3} + 147 a^{2} b + 21 a b^{2} + 1 \cdot {(b)}^{3}$

Step 4.17

Multiply ${(b)}^{3}$ by $1$ .

$343 a^{3} + 147 a^{2} b + 21 a b^{2} + b^{3}$