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# Linear equation y = k x + d

We concentrate on the meaning of k and d in the linear equation y = kx + d by trying different values for k and d. To do this we might enter the following lines in the input text field at the screen's bottom (press enter at the end of each line).

        k = 1
        d = 2
        y = k x + d

Now we can change k and d in the algebra window (right click: "Edit") or in the input text field

        k = 2
        k = -3
        d = 0
        d = -1

You can change k and d very easily with the arrow keys (animation, 4.1.2) or sliders (right click on k or d, Show Object; see 3.2.10).

In a similar way we might investigate the equations of conic sections such as x2/a2 + y2/b2 = 1, b2x2 + a2y2 = a2b2 or (x - m)2 + (y - n)2 = r2.