Pleaseee cab someone help me out with this maths question

Y is directly proportional to the square of x.
When x=3, y=18. Calculate value of x when y=50

Reply 1

Y is directly proportional to the square of x.
When x=3, y=18. Calculate value of x when y=50

Y=kx^2
18=k(3)^2
k=2 (after dividing both sides by 9)

therefore Y=2x^2

50 = 2(x)^2
25 = x ^2 (divided by 2 and then take the square root of 25)
x = ±5

Reply 2

Abithegoat

Hehe. Slow down buddy. I am normally good at these type of questions but the power (^2) is throwing me off. And why are there 2 values?

Reply 3

davros

Original post by R3Ni

Y=kx^2
18=k(3)^2
k=2 (after dividing both sides by 9)
therefore Y=2x^2
50 = 2(x)^2
25 = x ^2 (divided by 2 and then take the square root of 25)
x = ±5

I'll let it go here, but please note that it is against forum rules to post full solutions - please stick to hints in future :smile:

Original post by Abithegoat

Hehe. Slow down buddy. I am normally good at these type of questions but the power (^2) is throwing me off. And why are there 2 values?

As per the above, you're told that y is proportional to the square of x, which means that you can write down y = kx^2. Are you happy with that as the starting point?

Reply 4

R3Ni

Original post by davros

I'll let it go here, but please note that it is against forum rules to post full solutions - please stick to hints in future :smile:

As per the above, you're told that y is proportional to the square of x, which means that you can write down y = kx^2. Are you happy with that as the starting point?

Hi there, my bad! I’m a new user, thanks for letting me know :smile:

Reply 5

Abithegoat

Original post by davros

I'll let it go here, but please note that it is against forum rules to post full solutions - please stick to hints in future :smile:

As per the above, you're told that y is proportional to the square of x, which means that you can write down y = kx^2. Are you happy with that as the starting point?

Says who davros? It's against the rules to help people... I am confused

Reply 6

Abithegoat

Original post by davros

I'll let it go here, but please note that it is against forum rules to post full solutions - please stick to hints in future :smile:

As per the above, you're told that y is proportional to the square of x, which means that you can write down y = kx^2. Are you happy with that as the starting point?

Ohhhhhh!!!!! I understand nowwww I wrote it as square root of x! Thanks guys.

Reply 7

davros

Original post by Abithegoat

Says who davros? It's against the rules to help people... I am confused

It's not against the rules to "help" people, but it is against the rules to post full solutions. Here is a link to the posting guidelines for this forum:
**Posting Guidelines** - The Student Room

Most people can find solutions for themselves with a little nudge in the right direction or a few hints - as I think you've realised now with this question :smile: