Question

Variable y^2 varies directly with x2, and y = 18 when x = 6.



Which graph represents the quadratic variation?
A.http://static.k12.com/calms_media/media/1540000_1540500/1540310/1/e704306724d0e3058f5f975d02ad64262eb5d886/MS_ALG_S2_01_12_quiz_Q5a_question.gif
B.http://static.k12.com/calms_media/media/1540000_1540500/1540311/1/d3c9c95d917ce7280f5dbce58d52cc1b289e4903/MS_ALG_S2_01_12_quiz_Q5b_question.gif
C.http://static.k12.com/calms_media/media/1540000_1540500/1540312/1/520c64d5cf628a3b4b22b816792234a7675902b7/MS_ALG_S2_01_12_quiz_Q5c_question.gif
D.http://static.k12.com/calms_media/

Answer 1

D. http://static.k12.com/calms_media/media/1540000_1540500/1540313/1/69f31c1a860fc344187f2804ec831319d4f09b69/MS_ALG_S2_01_12_quiz_Q5d_question.gif

Answer 2

@campbell_st

Answer 3

@pitamar thank you btw

Answer 4

Ok, what bothers me is that \(y^2\) is not a variable... \(y\) is.
The answers also make a little sense, because even if \(y^2\) would vary directly with \(x^2\) then we could say:
$$
y^2 = a \cdot x^2 \\
y =\pm\sqrt{a \cdot x^2 } \\
y = \pm\sqrt{a} \cdot x
$$
Which wouldn't result in a graph of a parabola...
Are you sure the question is correct?

Answer 5

Variable y varies directly with x^2, and y = 18 when x = 6.

Which graph represents the quadratic variation?

Thats it

Answer 6

@pitamar

Answer 7

Ok so B

Answer 8

Now that makes more sense.
That would mean we have something of the form:
$$y=a \cdot x^2$$
We know that the following has to work out:
$$x=6 \implies y=18 \\
18=a \cdot (6)^2 \\
18=a \cdot 36 \\
a=\frac{18}{36}=\frac{\cancel{18}}{\cancel{18} \cdot 2}=\frac{1}{2}$$

So plugging it in we get:
$$ y=\frac{1}{2}x^2 $$
Now let's take a point shown in the graph, like x=2
$$x=2 \implies y=\frac{1}{2}\cdot(2)^2=\frac{1}{2}\cdot 4=2$$

Answer 9

ye

Answer 10

Thanks =)

Answer 11

No problem

Answer 12

I have 1 more could you help?