help wanted with math Q (1 Viewer)

[frankenstein]

I have a test tommrrow morining and i need HELP!

so can some one please give me an explanation and answer to the folowing question? =]


What values can a take in these expressions?


sq rt a - 4 = 0

Its a parabola question...so please gimme sum explanation to this.

 

[frankenstein]

this question can be viewd in the new signpost math text book, page 323, q3-a.

i await yo help!

 

[SoulSearcher]

Is it sqrt(a-4) = 0, or sqrt(a) - 4 = 0?
for the first one, a = 4, and for the second one, a = 16.

 

[xlr8-crillz]

lol, like that was hard.

 

[SoulSearcher]

Bump up the thread for that comment?

 

[z600]

[FONT=宋体][FONT=宋体][FONT=宋体]I dont see how it's a quadratic equation, whether the
[FONT=宋体]√ includes the (a-4) or not . I graph both cases on a graph calculator, looks nothing like a parabola. [/FONT]
[/FONT][FONT=宋体][/FONT]
[/FONT][/FONT]

 

[SoulSearcher]

Threadstarter must have been mistaken or something.

 

[xlr8-crillz]

Bump up the thread for that comment?

didnt plan on that

[FONT=宋体][FONT=宋体][FONT=宋体]I dont see how it's a quadratic equation, whether the
[FONT=宋体]√ includes the (a-4) or not . I graph both cases on a graph calculator, looks nothing like a parabola. [/FONT]
[/FONT]
[/FONT][/FONT]

What does it look like??

I seriously dont know!

 

[Riviet]

It's half a parabola.

Replace "a" with "x" and turn it into a cartesian equation:

y=sqrt(x-4)

This is a half of a sideways parabola, the half taken is the upper one because that half has all the positive y-values.

Justification that it's a sideways parabola:
y²=x-4 (squaring both sides)
x=y²+4

To sketch this:
Graph y=x²+4 in pencil.
x=y²+4 is a reflection of y=x²+4 in the line y=x (inverse function) - sketch this inverse function.
Since y can only be positive in y=sqrt(x-4), rub out the bottom half of your sideways parabola. This leaves you with the sideways half parabola.

 

[xlr8-crillz]

It's half a parabola.

Replace "a" with "x" and turn it into a cartesian equation:

y=sqrt(x-4)

This is a half of a sideways parabola, the half taken is the upper one because that half has all the positive y-values.

Justification that it's a sideways parabola:
y²=x-4 (squaring both sides)
x=y²+4

To sketch this:
Graph y=x²+4 in pencil.
x=y²+4 is a reflection of y=x²+4 in the line y=x (inverse function) - sketch this inverse function.
Since y can only be positive in y=sqrt(x-4), rub out the bottom half of your sideways parabola. This leaves you with the sideways half parabola.

You Genius!!

yeh i get it now after u put it into y=sqrt(x-4), but is this how you would figure out all equations with different values, e.g. the one above where u just replace the pronumeral with x and solve.

 

[frankenstein]

Nevermind, I failed that test.

Been ages, stuff it!

 

[Aerath]

LOL - taking a stroll down memory lane?