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Y= (x- 3) (x+5)

Find vertex, min or max, X-intercepts, and Y- intercepts
Show your work please!

User S Krishna
by
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1 Answer

5 votes
First, you want to do the FOIL method to expand the the equation. You get:

y = x² + 2x - 15

Now to find the vertex, you use this equation:

Vertex: x = - b / 2a
where the equation is in the form y = ax² + bx + c. Plug in the information needed given by this new equation.

x = - 2 / 2(1)
= - 2 / 2
= - 1

Now we plug in - 1 for x.

y = (- 1)² + 2(- 1) - 15
y = 1 - 2 - 15
y = - 1 - 15
y = - 16.

Your vertex is (- 1, - 16).

For the y-intercept, plug in zero for x and solve.
y = (0)² + 2(0) - 15
y = 0 + 0 - 15
y = - 15.

Your y-intercept is (0, - 15).

For the x-intercept, plug in zero for y and solve. Easy way to do this is just plug it into your original equation and set each binomial equal to zero.
x - 3 = 0
x = 3

x + 5 = 0
x = - 5.

Your x-intercepts are at (- 5, 0) and (3, 0).

Graph included for proof of these answers.
Y= (x- 3) (x+5) Find vertex, min or max, X-intercepts, and Y- intercepts Show your-example-1
User Yassir Irfan
by
8.6k points

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