Is y-x=4 a direct variation equation?

2 Answers
Alan P.
Apr 9, 2015

No.
A direct variation equation has the form or can be converted into the form:
y = mx for some constant value m

One observation that follows from this is that if x=0 then y=0;
this condition is clearly not true for the given equation.

A second observation is that for a direct variation equation doubling the value of x (or multiplying it by any value) causes the value of y to be multiplied by that same value;
again this is not true for the given equation.

Meave60
Apr 9, 2015

No. A direct variation equation defines a line that goes through the origin, (0,0).

y-x=4 does not satisfy that requirement.

The equation in slope-intercept form is y=x+4. If x=0, then y=4. So this equation is not a direct variation.

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