If y varies directly to x, then y = kx, where k is called the constant of variation. When x = -2 and y = 5, we have:
y = kx
5 = -2k
k = -5/2
Thus, y = -(5/2)x.
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No, y+2=x does not show direct variation. In direction variation you need to be able to multiply y by something to get x. In the question y+2=x, you have to add 2 to y to get x, which is not multiplying.)
y=3x is a direct variation in that y varies directly with x by a factor of 3. Any linear equation (a polynomial of degree 1, which is a polynomial equation with a highest exponent of 1), is a direct variation of y to x by some constant, and this constant is simply the coefficient of the "x" term. Other examples: y=(1/2)x is a direct variation, and the constant of variation is 1/2 y=-9x is a direct variation, and the constant of variation is -9
No, this is an inverse variation.
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Both are variations of certain kinds of equations. X=kY is a direct variation since X varies directly as Y and k is the constant of variation. X=k/Y is an inverse variation where X varies inversly as Y and k is the constant of variation. Both of these variations are also functions.