Question

What are the coordinates of the vertex of the graph of the function y = –3x² –12x + 3?




(–2, 29)
(2, –15)
(2, –9)
(–2, 15)

Answer 1

As with the previous one, calculate the x-coordinate with the formula x = -b/(2a).
As you can see, a = -3 and b = -12.

Put that x-value in y = –3x² –12x + 3 and out comes your y-value of the vertex.

It is the same routine every time!

Answer 2

but I can't do it! It's so hard for me!!!

Answer 3

Come on, that can't be true. Let's do it together:

\(x=-\dfrac{b}{2a}=-\dfrac{-12}{2 \cdot -3}=...\)

What number do you get?

Answer 4

-6

Answer 5

How much is \(-\dfrac{-12}{-6}\)?

Answer 6

6

Answer 7

Try again please...

Answer 8

it is: \(-\dfrac{12}{6}\)=...

Answer 9

18???????

Answer 10

Ignore the first minus-sign. Then you have -12 divided by -6, so that is the same as 12/6.

How much is 12/6

Answer 11

it is 6

Answer 12

or 2

Answer 13

6 or 2, only one can be right!

So it is 2.

Now remember, we still have that first minus-sign, so we've found: x=-2.

Now you have to set x=-2 in the equation: y = –3x² –12x + 3 to get y.

Answer 14

@iloveyooh: YW!

Answer 15

THANK YOU!