stuck on this and answer is wrong

Question

Find the vertex of the parabola

x coordinate = y coordinate =  

Graph this function and estimate the x intercepts to the nearest tenth. 

Show the answers separated by a comma = 

 

Answer 1

The function y = - 4x²  + 12x + 6

Compare it to parabola equation y = ax²  + bx + c.

a = - 4, b = 12, c = 6

Axis of symmetry x = - b/2a

x = (-12)/2(-4) = 12/8

x = 1.5

Substitute x = 1.5 in y = - 4x²  + 12x + 6.

y = - 4(1.5)²  + 12(1.5) + 6

y =  - 9 + 18 + 6

y = 15

Vertex of parabola is (x, y) = (1.5, 15).

To find y intercepts substitute x = 0 in y = - 4x²  + 12x + 6.

y = - 4(0)²  + 12(0) + 6

y = 6

To find x intercepts substitute y = 0 in y = - 4x²  + 12x + 6.

x intercepts are

Answer 2

Contd...

x intercepts are - 0.4 and 3.4.

To graph the function we need some more points to accurate graph.

y	y = - 4x2  + 12x + 6	(x, y)
1	y = - 4(1)2  + 12(1) + 6 = 14	(1,14)
2	y = - 4(2)2  + 12(2) + 6 = 14	(2,14)
0	y = - 4(0)2  + 12(0) + 6 = 6	(0,6)
3	y = - 4(3)2+12(3)+6	(3,6)

Graph

Draw a coordinate plane.

Plot the vertex and axis of symmetry.

Plot the x ,y intercepts, points found in the table.

Connect the points with smooth curve.