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sapphers
Group Title
Determine whether y varies directly with x. If so find the constant of variation k and write the equation.
x y
7 11
8 13
9 15
10 17
Can someone please help me and explain
 one year ago
 one year ago
sapphers Group Title
Determine whether y varies directly with x. If so find the constant of variation k and write the equation. x y 7 11 8 13 9 15 10 17 Can someone please help me and explain
 one year ago
 one year ago

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jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.2
If y varied directly with x, then y = k*x for some fixed constant number k
 one year ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.2
Using this info, what is k?
 one year ago

sapphers Group TitleBest ResponseYou've already chosen the best response.0
I don't know. How do you find it? I really don't understand this.
 one year ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.2
The idea is that if you multiply each x term by some fixed number (the same fixed number) and you get the corresponding y value, then this is a direct variation Here's a simple example x y  1 2 2 4 3 6 If we multiply each x by 2 we'll get the correct corresponding y value, so this is a direct variation
 one year ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.2
y = k*x 11 = k*7 Now solve for k
 one year ago

sapphers Group TitleBest ResponseYou've already chosen the best response.0
Oh that makes more sense! Okay (:
 one year ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.2
So what is k when you solve that last equation?
 one year ago

sapphers Group TitleBest ResponseYou've already chosen the best response.0
Could I do 11/7? K=1.57
 one year ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.2
So if this was a direct variation, then we should be able to multiply each x by 11/7 or roughly 1.57 to get the corresponding y value But... When x = 8, k*x is (11/7)*8 = 88/7 which is roughly 12.57 and NOT 13 So this can't be a direct variation
 one year ago

sapphers Group TitleBest ResponseYou've already chosen the best response.0
Since it's not, what am I supposed to do? Just leave it like that or..
 one year ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.2
Just say it's not a direct variation. If it was a direct variation, then you would proceed to find k or show/say what k is.
 one year ago

sapphers Group TitleBest ResponseYou've already chosen the best response.0
Oh alright
 one year ago

jim_thompson5910 Group TitleBest ResponseYou've already chosen the best response.2
since it says "If so find the constant of variation k and write the equation"
 one year ago

tcarroll010 Group TitleBest ResponseYou've already chosen the best response.0
jim is right and he proved that there is no direct constant for proportionality between y and x, so you don't have to do anything else but state that. There IS an equation (actually lots of them) that you could write to show a relationship between y and x, but you are not required to find one since none will exhibit a directly proportional relationship between y and x.
 one year ago
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