choiheesung97
Badges: 2
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#1
Report Thread starter 4 years ago
#1
y is directly proportional to x^2.
When x = 3, then y = 36.
a) Express y in terms of x.

z is inversely proportional to x.
When x = 4, z = 2.
b) Show that z = c y^n , where c and n are numbers and c > 0.

You must find the values of c and n.
0
reply
Loci Pi
Badges: 16
Rep:
? You'll earn badges for being active around the site. Rep gems come when your posts are rated by other community members.
#2
Report 4 years ago
#2
(Original post by choiheesung97)
y is directly proportional to x^2.
When x = 3, then y = 36.
a) Express y in terms of x.

z is inversely proportional to x.
When x = 4, z = 2.
b) Show that z = c y^n , where c and n are numbers and c > 0.

You must find the values of c and n.
a) y = kx^2
36 = (3^2)k
Now you just need to find k and substitute it back into the equation in the first line of my working out.
Spoiler:
Show

k= 36/9 =4
y = 4x^2


b) z = k/x
2 = k/4
Now find k
Spoiler:
Show

k= 2 x 4 = 8


Rearrange and substitute the equations into each other until they are in the form z = cy^n
z= 8/x
x = 8/z
Spoiler:
Show

x^2 = 64/z^2
y= 4(64/z^2)
y= 256/z^2
z^2 = 256/y
z = square root (256/y)
z = 16/ (y^0.5)
z = 16 y^(-0.5)

c = 16
y = -0.5


I have probably make a silly mistake somewhere but I enjoyed this question
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

Y13's - If you haven't confirmed your firm and insurance choices yet, why is that?

I am waiting until the deadline in case anything in my life changes (22)
20.56%
I am waiting until the deadline in case something else changes (e.g. exams/pandemic related concerns) (12)
11.21%
I am waiting until I can see the unis in person (7)
6.54%
I still have more questions before I make my decision (18)
16.82%
No reason, just haven't entered it yet (25)
23.36%
Something else (let us know in the thread!) (23)
21.5%

Watched Threads

View All