Question

Where is the vertex of the parabola? y = x2 + 2x – 3 Above the x-axis Below the x-axis On the x-axis On the y-axis

Answer 1

The x coordinate of the vertex can be found by using the formula -b/2a for a quadratic in standard form.

Answer 2

And the y coordinate from substituting that value back in for x and solving for y.

Answer 3

So, what do you get for the x coordinate of the vertex?

Answer 4

i am stil not sure @JoannaBlackwelder

Answer 5

Can you identify a, b, and c?

Answer 6

no

Answer 7

ax^2 + bx + c

Answer 8

So, a is 1, b is 2, and c is -3

Answer 9

Do you see how I got those numbers?

Answer 10

i think so

Answer 11

They are the coefficients of each term in the quadratic.

Answer 12

So, can you try to plug those numbers into the formula I gave?

Answer 13

ax^2 + bx + c = 1x^2 + 2x + -3

Answer 14

So, that is the expression given in the problem. Do you see how that is the same?

Answer 15

The formula I was meaning is the -b/2a for the x coordinate of the vertex.

Answer 16

-2/2^1

Answer 17

Close, -2/2*1

Answer 18

So, that simplifies to -1

Answer 19

And that is the x coordinate of the vertex. :-)

Answer 20

ok

Answer 21

Now we need to find the y coordinate to find the specific point.

Answer 22

We do that by subbing in the -1 into x into the expression.

Answer 23

(-1)^2 + 2(-1) - 3

Answer 24

See how I did that?

Answer 25

yes

Answer 26

:-) So, what does that simplify to?

Answer 27

-4

Answer 28

Right! So, what is the coordinate of the vertex?

Answer 29

-1,-4

Answer 30

Sweet. So, is that above, below, or on the axes?

Answer 31

below

Answer 32

:-)

Answer 33

Thanks so much!

Answer 34

You're welcome!