SOLUTION: Graph y=3x^2 -12x-3 Then state the vertex. Please help me with this problem

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Question 978084: Graph y=3x^2 -12x-3
Then state the vertex.
Please help me with this problem
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
+y=3x%5E2+-12x-3+
to graph it, you need several points
so, make a table
x|y......choose several values for x and calculate y
-1|12....+y=3%2A%28-1%29%5E2+-12%28-1%29-3=3%2A1%2B12-3=12+
0|-3....+y=3%2A%280%29%5E2+-12%280%29-3=-3+

1|-12....+y=3%2A%281%29%5E2+-12%281%29-3=3%2A1-12-3=-12+
2|-15....+y=3%2A%282%29%5E2+-12%282%29-3=12-24-3=-12-3=-15+
3|-12....+y=3%2A%283%29%5E2+-12%283%29-3=27-36-3=-12+
plot these points and draw a parabola through:



compare +y=3x%5E2+-12x-3+ to +y=ax%5E2+%2Bbx%2Bc+, you see that a=3 and b=-12
since the x coordinate of the vertex is -b%2F2a, we have
-b%2F2a=-%28-12%29%2F%282%2A3%29=12%2F6=2
so,x=2
substitute it in +y=3x%5E2+-12x-3+ and calculate the y coordinate of the vertex
+y=3%2A%282%29%5E2+-12%282%29-3
y=12-24-3
y=-12-3
y=-15+
so, the vertex is at (2,-15)