Which of the following has a constant of proportionality of 2? A) y = 2x B) y = x + 2 C) 2y = x D) y + 2 = 2x
2 answers:
The correct answer is A.
You have direct variation if x and y are modeled by the equation
In this case, m is the constant of proportionality. So, if the constant has to be 2, the equation becomes
A side note: Actually, option C has a constant of proportionality of two as well, except the roles of x and y are interchanged. I chose option A because usually you want the y = mx form, but the names of the variables are obviously meaningless.
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