Mathematics

Lilianna Underwood

14 November, 22:14

Jan'ai was asked to determine the minimum for a function with zeros located at - 1 and 5, which also has a y-intercept of

(0, - 25). Her work is shown.

Begin to write a function in factored form. f (x) = a (x + 1) (x - 5)

Substitute to determine a.

1-25 = a (0+1) (0-5)

Simplify and solve to find a.

-5

Rewrite the function.

f (x) = 5 (x+1) (x-5)

Rewrite in standard form.

.

f (x) = 5x2-20x-25

Find the x-coordinate of the vertex.

-20 - 20. y_

^ 2 (5) - 10

Find the y-coordinate of the vertex. y=5x2-20x-25

y=5 (-2) 2 - 20 (-2) - 25

y=35 so (-2,35)

Which best describes the first error in Jan'ai's work?

O

She incorrectly determined the factors for the beginning function.

She incorrectly determined the a value.

She incorrectly transformed the equation to standard form.

O