What is the vertex of #y= (x − 3)(4x + 2) #?

1 Answer
Jun 17, 2018

Vertex is at #(1.25 , -12.25)#

Explanation:

# y=(x-3)(4 x+2) or y= 4 x^2 -10 x -6#

# a= 4 , b= -10 ,c =-6 ; [y= ax^2+bx+c#

Vertex ( x coordinate) is # v_x= (-b)/(2 a)=10/8=1.25 #

Putting #x=1.25# in the equation we get #v_y#

Vertex ( y coordinate) is

# v_y= 4 *1.25^2-10 *1.25-6=-12.25#

Vertex is at #(1.25, -12.25)#

graph{y=(x-3)(4x+2) [-40, 40, -20, 20]} [Ans]