Precalculus Examples

$x^{2} - 8 x + 16$

Step 1

Write $x^{2} - 8 x + 16$ as an equation.

$y = x^{2} - 8 x + 16$

Step 2

Find the x-intercepts.

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Step 2.1

To find the x-intercept(s), substitute in $0$ for $y$ and solve for $x$ .

$0 = x^{2} - 8 x + 16$

Step 2.2

Solve the equation.

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Step 2.2.1

Rewrite the equation as $x^{2} - 8 x + 16 = 0$ .

$x^{2} - 8 x + 16 = 0$

Step 2.2.2

Factor using the perfect square rule.

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Step 2.2.2.1

Rewrite $16$ as $4^{2}$ .

$x^{2} - 8 x + 4^{2} = 0$

Step 2.2.2.2

Check that the middle term is two times the product of the numbers being squared in the first term and third term.

$8 x = 2 \cdot x \cdot 4$

Step 2.2.2.3

Rewrite the polynomial.

$x^{2} - 2 \cdot x \cdot 4 + 4^{2} = 0$

Step 2.2.2.4

Factor using the perfect square trinomial rule $a^{2} - 2 a b + b^{2} = {(a - b)}^{2}$ , where $a = x$ and $b = 4$ .

${(x - 4)}^{2} = 0$

Step 2.2.3

Set the $x - 4$ equal to $0$ .

$x - 4 = 0$

Step 2.2.4

Add $4$ to both sides of the equation.

$x = 4$

Step 2.3

x-intercept(s) in point form.

x-intercept(s): $(4, 0)$

Step 3

Find the y-intercepts.

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Step 3.1

To find the y-intercept(s), substitute in $0$ for $x$ and solve for $y$ .

$y = {(0)}^{2} - 8 \cdot 0 + 16$

Step 3.2

Solve the equation.

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Step 3.2.1

Remove parentheses.

$y = 0^{2} - 8 \cdot 0 + 16$

Step 3.2.2

Remove parentheses.

$y = {(0)}^{2} - 8 \cdot 0 + 16$

Step 3.2.3

Simplify ${(0)}^{2} - 8 \cdot 0 + 16$ .

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Step 3.2.3.1

Simplify each term.

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Step 3.2.3.1.1

Raising $0$ to any positive power yields $0$ .

$y = 0 - 8 \cdot 0 + 16$

Step 3.2.3.1.2

Multiply $- 8$ by $0$ .

$y = 0 + 0 + 16$

Step 3.2.3.2

Simplify by adding numbers.

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Step 3.2.3.2.1

Add $0$ and $0$ .

$y = 0 + 16$

Step 3.2.3.2.2

Add $0$ and $16$ .

$y = 16$

Step 3.3

y-intercept(s) in point form.

y-intercept(s): $(0, 16)$

Step 4

List the intersections.

x-intercept(s): $(4, 0)$

y-intercept(s): $(0, 16)$

Step 5