Hannah wishes to find the vertex of the function x2 + 3x - 28 = 0 by completing the square. Which of the following equations may be used to identify the coordinates of the vertex? A.
(x + 1.5)2 = 30.25

B.
(x + 2.25)2 = 30.5

C.
(x + 2.5)2 = 30.75

D.
(x + 2.75)2 = 32.5

Question

Hannah wishes to find the vertex of the function x2 + 3x - 28 = 0 by completing the square. Which of the following equations may be used to identify the coordinates of the vertex?    A.
(x + 1.5)2 = 30.25

B.
(x + 2.25)2 = 30.5

C.
(x + 2.5)2 = 30.75

D.
(x + 2.75)2 = 32.5

campbell_st · Answer

well to start hannah should have 

$$y = x^2 + 3x - 28 $$

as that is a parabola

so look at the equation and split it into terms in x and the constant

$$y = (x^2 + 3x) - 28$$

to complete the square in x, you need to find half of 3, then square it. 

add it inside the brackets and subtract it outside the brackets.... 

hope that helps