How do I use the vertex formula to determine the vertex of the graph for y = -4x^2 + 8xy=4x2+8x?

1 Answer
May 1, 2015

The vertex of graph of y=ax^2+bx+cy=ax2+bx+c

has xx-coordinate x=-b/(2a)x=b2a

So, the xx-coordinate of the vertex of the graph of y=-4x^2+8xy=4x2+8x is:

x= -(8)/(2(-4)x=82(4), which we can evaluate (simplify, calculate)

x= -(8)/(2(-4)) = -8/-8 = 1x=82(4)=88=1,

To find the yy-coordinate of the vertex, find the value of yy, when x=1x=1

y = -4(1)^2 +8(1) = -4 + 8 = 4y=4(1)2+8(1)=4+8=4

The vertex is: (1, 4)(1,4).