Question

What is the x-coordinate of the vertex of the parabola whose equation is y = 3x2 + 9x?

Answer 1

Hello :
y = 3x²+9x
   = 3(x² + 3x )
   = 3 ( x² +2(3/2)x +(3/2)²) -(3/2)²)
   = 3((x+3/2)² -9/4)
y = 3 (x+3/2)² -27/4
the x-coordinate of the vertex  is : - 3/2

Answer 2

Answer:

$\text{The x-coordinate of vertex of parabola is -1.5}$      

Step-by-step explanation:

Given the equation of parabola

$y=3x^2+9x$

we have to find the x-coordinate of the vertex of the parabola.

The general form of equation of parabola is

$ax^2+bx+c=0$

The x-coordinate of the vertex of the parabola can be calculated as

$h=\frac{-b}{2a}$

Comparing the given equation with the general equation, we get

a=3, b=9, c=0

x-coordinate of the vertex of the parabola is

$h=\frac{-9}{2(3)}=\frac{-3}{2}=-1.5$

The x-coordinate of vertex of parabola is -1.5