Question

1. Find the vertex of y = – x2 - 4x + 5

Answer 1

(- 2, 9 )

Explanation:

Given a parabola in standard form, y = ax² + bx + c : a ≠ 0

Then the x- coordinate of the vertex is

`x_(vertex)` = -
`(b)/(2a)`

y = - x² - 4x + 5 ← is in standard form

with a = - 1 and b = - 4, thus

`x_(vertex)` = -
`(-4)/(-2)` = - 2

Substitute x = - 2 into equation for corresponding y- coordinate

y = - (- 2)² - 4(- 2) + 5 = - 4 + 8 + 5 = 9

vertex = (- 2, 9 )