Quadratic funtion

[SONCEE]

F(x)=x^2+4x
find the x and y intercepts of this parabola and it's vertex

 

[chivox]

What's your question, Soncee? Can you look in your textbook and provide some other examples that look like this, and then try to work this one out? If you show your steps in solving this one, I'm sure we can see where you're stuck and help you a lot better.

 

[Deleted member 4993]

F(x)=x^2+4x
find the x and y intercepts of this parabola and it's vertex

If you have a quadratic equation of the form

y = a(x - h)^2 + k

then it represents a parabola with the vertex at (h,k).

What are the definitions of x-intercept and y-intercept?

Please show us your work, indicating exactly where you are stuck - so that we know where to begin to help you.

 

[SONCEE]

f(x)=x^2+4x

i did this

x=-b
2a

-4
2(1) = -2

p(-2) =-2^2+4(2)
4+-8= -4
x=-4 y=-2 vertex is -4,4 parabola opens upward

 

[mmm4444bot]

x=-b/(2a) Please type parentheses around denominators that have more than one character.

x = -4/(2) = -2

p(-2) = (-2)^2 + 4(-2)

Somehow, the function name changed from F to p?

Please type parentheses around a negative number when squaring (-2)^2

Also, you forgot a negative sign on the last term, above, although you got the right product, below.

4 + -8 = -4

x=-4 y=-2 vertex is -4,4

Your plan is good, but your execution crashed and burned.

The formula gives the x-coordinate of the vertex.

x = -b/(2a)

You arrived at x = -2 and y = -4, but then you wrote y = -2 and you also wrote (-4, 4) as the location of the vertex.

I'm not sure why you gave x = -2 and x = -4. There is only one x-coordinate at the vertex.

I'm not sure why you gave y = -4, y = -2 and y = 4. There is only one y-coordinate at the vertex.

Perhaps, you are just a sloppy typist. If not, then slow down, try again, be careful, and check your results.

 

[SONCEE]

f(x)=x^2+4x



-4
2(1) = -2 =x

p(-2)= (-2)^2+4(-2)= -4=y

vertex= -2,-4
parabola slopes up

 

[chivox]

f(x)=x^2+4x

vertex= -2,-4
parabola slopes up

Looks right to me, plus or minus a few steps, but it looks good so far. Now do you know how to find the two points where this graph crosses the x axis and the one point where it crosses the y axis? Or was that not what the question was?

A hint is to think about what the values of x and y are at those points and solve the quadratic equation for those. And be careful with the arithmetic on this one.