Question

The x-intercept of the function f(x)=x^2-81

Answer 1

Answer:

x=9

x=-9

Step-by-step explanation:

The x intercept or roots are x values that makes the f(x) equal 0. So in order words, to find the x intercept. Set the equation equal 0.

${x}^{2} - 81 = 0$

We can approach this problem 2 ways

Way 1: Differnece of Squares

Recall that

$a {}^{2} - {b}^{2} = (a + b)(a - b)$

Since x^2 and 81 are both perfect squares and 81 is negative, we can say that

$(x + 9)(x - 9) = 0$

Set each equation to zero

$x = 9$

$x = - 9$

Way 2: Take square root of both sides

${x}^{2} - 81 = 0$

${x}^{2} = 81$

Next step, take square root of both sides. Square root produce negative and positive solutions so

$x = 9$

or

$x = - 9$

Answer 2

Answer:

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