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

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

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=(-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=(-9)/(2(3))=(-3)/(2)=-1.5`

The x-coordinate of vertex of parabola is -1.5