Using the vertex of the quadratic equation, it is found that the value of b is of -9.
A quadratic equation is modeled by:
[tex]y = ax^2 + bx + c[/tex]
The vertex is given by:
[tex](x_v, y_v)[/tex]
In which:
[tex]x_v = -\frac{b}{2a}[/tex]
[tex]y_v = -\frac{b^2 - 4ac}{4a}[/tex]
The axis of symmetry is [tex]x = x_v = -\frac{b}{2a}[/tex].
Considering the coefficient a, we have that:
In this problem, we have that the function is defined as follows:
[tex]f(x) = 3x^2 + bx + 4[/tex]
We have that [tex]a = 3, x_v = \frac{3}{2}[/tex], hence the value of b is found as follows:
[tex]x = -\frac{b}{2a}[/tex]
[tex]\frac{3}{2} = -\frac{b}{6}[/tex]
b = -6 x 3/2
b = -9.
More can be learned about the vertex of a quadratic equation at https://brainly.com/question/24737967
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