Answers
B, D and E are proportional
A, C, and F are not proportional
y = 3+x .... not proportional
y = 1.6x .... proportional
y = 3/(4x) .... not proportional
y = x .... proportional
y = 12x .... proportional
y = 2x+1 ... not proportional
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Explanations:
Anything in the form y = k*x is a direct proportional equation. As x goes up, so does y. The same happens if x decreases, and we'll have y also decrease. They go up together or down together. This is where the "direct" comes from. Specifically they change the same amount each time (hence the term "proportional").
For something like y = 1.6x, we have k = 1.6
In the equation y = x, we have y = 1x in reality so k = 1 here.
Lastly, y = 12x has k = 12.
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The other equations are not in the form y = kx. Whenever we have y = mx+b, with b nonzero, then y = mx+b is not proportional. The value of b must be 0 for it to fit y = kx form. This rules out y = 2x+1 and y = 3+x or y = x+3.
The equation y = 3/(4x) is an inversely proportional equation in the form y = k/x. It cannot be written as y = kx. Note how x is in the denominator for y = 3/(4x) while the same can't be said for y = kx. Inversely proportional equations have x increase and y decrease, or vice versa. They go in opposite directions.