Answer
See the graph
![](https://gradesaver.s3.amazonaws.com/uploads/solution/48d83f6d-fc4e-4eb1-8729-3278449e8698/result_image/1599814184.png?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAJVAXHCSURVZEX5QQ%2F20240908%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20240908T001312Z&X-Amz-Expires=900&X-Amz-SignedHeaders=host&X-Amz-Signature=f445f9ac82e24dea6d16565b20beaeef0f80a1170bfb6b811bdb6c2efc63654a)
Work Step by Step
$y=3x(x+4)$
$y=3x^2+12x$
The function is in quadratic form $y=ax^2+bx+c$
with $a=3, b=12, k=0$
Find the x-coordinate: $x=-\frac{b}{2a}=-\frac{12}{2.3}=-2$
Substitute for x: $y=3(-2)^2+12(-2)=-12$
The vertex is $(-2,-12)$
Also the axis of symmetry is $x=-2$
Find some other points:
$x=-4 \rightarrow y=0$
$x=0 \rightarrow y=0$
$x=1 \rightarrow y=15$
$x=-5\rightarrow y=15$