Question

I need help understanding direct linear variation.


Which does not show a direct variation between x and y?

A. y=5x


B. y=6/x


C. y=0.7x


D. y=x/9

Answer 1

@Directrix @mathmale

Answer 2

direct variation is in the form

y = k*x

in words

(some variable) = (some constant) times (some other variable)

Answer 3

so some examples would be

y = 2*x

y = 10*x

y = 5.3*x

y = (1/2)*x

notice how they all fit the form y = k*x.

Answer 4

does that make sense?

Answer 5

so would the answer be D? since the constant and variable are flipped?

Answer 6

D is a trick thrown at you

y=x/9 is the same as y = (1/9)*x

it's similar to saying (1/2)*3 = 3/2

Answer 7

y = (1/9)*x is in the form y = k*x where k = 1/9

Answer 8

Ohhh so in that case, would it be B?

Answer 9

yes because y = 6/x cannot be written into the form y = k*x

it's actually in the form y = k/x which is inverse variation

Answer 10

Okay great, I think I got it now. Thank you so much! i'll tag you if I need more help with direct variation.

Answer 11

you're welcome