Precalculus Examples

${(x - 2 y)}^{4}$

Step 1

Pascal's Triangle can be displayed as such:

$1$

$1 - 1$

$1 - 2 - 1$

$1 - 3 - 3 - 1$

$1 - 4 - 6 - 4 - 1$

The triangle can be used to calculate the coefficients of the expansion of ${(a + b)}^{n}$ by taking the exponent $n$ and adding $1$ . The coefficients will correspond with line $n + 1$ of the triangle. For ${(x - 2 y)}^{4}$ , $n = 4$ so the coefficients of the expansion will correspond with line $5$ .

Step 2

The expansion follows the rule ${(a + b)}^{n} = c_{0} a^{n} b^{0} + c_{1} a^{n - 1} b^{1} + c_{n - 1} a^{1} b^{n - 1} + c_{n} a^{0} b^{n}$ . The values of the coefficients, from the triangle, are $1 - 4 - 6 - 4 - 1$ .

$1 a^{4} b^{0} + 4 a^{3} b + 6 a^{2} b^{2} + 4 a b^{3} + 1 a^{0} b^{4}$

Step 3

Substitute the actual values of $a$ $x$ and $b$ $- 2 y$ into the expression.

$1 {(x)}^{4} {(- 2 y)}^{0} + 4 {(x)}^{3} {(- 2 y)}^{1} + 6 {(x)}^{2} {(- 2 y)}^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4

Simplify each term.

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Step 4.1

Multiply ${(x)}^{4}$ by $1$ .

${(x)}^{4} {(- 2 y)}^{0} + 4 {(x)}^{3} {(- 2 y)}^{1} + 6 {(x)}^{2} {(- 2 y)}^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.2

Apply the product rule to $- 2 y$ .

$x^{4} ({(- 2)}^{0} y^{0}) + 4 {(x)}^{3} {(- 2 y)}^{1} + 6 {(x)}^{2} {(- 2 y)}^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.3

Rewrite using the commutative property of multiplication.

${(- 2)}^{0} x^{4} y^{0} + 4 {(x)}^{3} {(- 2 y)}^{1} + 6 {(x)}^{2} {(- 2 y)}^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.4

Anything raised to $0$ is $1$ .

$1 x^{4} y^{0} + 4 {(x)}^{3} {(- 2 y)}^{1} + 6 {(x)}^{2} {(- 2 y)}^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.5

Multiply $x^{4}$ by $1$ .

$x^{4} y^{0} + 4 {(x)}^{3} {(- 2 y)}^{1} + 6 {(x)}^{2} {(- 2 y)}^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.6

Anything raised to $0$ is $1$ .

$x^{4} \cdot 1 + 4 {(x)}^{3} {(- 2 y)}^{1} + 6 {(x)}^{2} {(- 2 y)}^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.7

Multiply $x^{4}$ by $1$ .

$x^{4} + 4 {(x)}^{3} {(- 2 y)}^{1} + 6 {(x)}^{2} {(- 2 y)}^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.8

Simplify.

$x^{4} + 4 x^{3} (- 2 y) + 6 {(x)}^{2} {(- 2 y)}^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.9

Rewrite using the commutative property of multiplication.

$x^{4} + 4 \cdot - 2 x^{3} y + 6 {(x)}^{2} {(- 2 y)}^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.10

Multiply $4$ by $- 2$ .

$x^{4} - 8 x^{3} y + 6 {(x)}^{2} {(- 2 y)}^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.11

Apply the product rule to $- 2 y$ .

$x^{4} - 8 x^{3} y + 6 x^{2} ({(- 2)}^{2} y^{2}) + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.12

Rewrite using the commutative property of multiplication.

$x^{4} - 8 x^{3} y + 6 \cdot {(- 2)}^{2} x^{2} y^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.13

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

$x^{4} - 8 x^{3} y + 6 \cdot 4 x^{2} y^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.14

Multiply $6$ by $4$ .

$x^{4} - 8 x^{3} y + 24 x^{2} y^{2} + 4 {(x)}^{1} {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.15

Simplify.

$x^{4} - 8 x^{3} y + 24 x^{2} y^{2} + 4 x {(- 2 y)}^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.16

Apply the product rule to $- 2 y$ .

$x^{4} - 8 x^{3} y + 24 x^{2} y^{2} + 4 x ({(- 2)}^{3} y^{3}) + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.17

Rewrite using the commutative property of multiplication.

$x^{4} - 8 x^{3} y + 24 x^{2} y^{2} + 4 \cdot {(- 2)}^{3} x y^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.18

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

$x^{4} - 8 x^{3} y + 24 x^{2} y^{2} + 4 \cdot - 8 x y^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.19

Multiply $4$ by $- 8$ .

$x^{4} - 8 x^{3} y + 24 x^{2} y^{2} - 32 x y^{3} + 1 {(x)}^{0} {(- 2 y)}^{4}$

Step 4.20

Multiply ${(x)}^{0}$ by $1$ .

$x^{4} - 8 x^{3} y + 24 x^{2} y^{2} - 32 x y^{3} + {(x)}^{0} {(- 2 y)}^{4}$

Step 4.21

Anything raised to $0$ is $1$ .

$x^{4} - 8 x^{3} y + 24 x^{2} y^{2} - 32 x y^{3} + 1 {(- 2 y)}^{4}$

Step 4.22

Multiply ${(- 2 y)}^{4}$ by $1$ .

$x^{4} - 8 x^{3} y + 24 x^{2} y^{2} - 32 x y^{3} + {(- 2 y)}^{4}$

Step 4.23

Apply the product rule to $- 2 y$ .

$x^{4} - 8 x^{3} y + 24 x^{2} y^{2} - 32 x y^{3} + {(- 2)}^{4} y^{4}$

Step 4.24

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

$x^{4} - 8 x^{3} y + 24 x^{2} y^{2} - 32 x y^{3} + 16 y^{4}$