Quadratics in the XC plane


by Kasey Nored


Our parent quadratic makes our familiar parabola.

y = ax2 + bx + c where b and c equal zero

Parent Function.JPG

The manipulation of a, b, and c shifts and dilates our parabola.

This write-up intends to explore the xc plane where c serves as y, for example to graph a point in the xc plane (x, c) would be the coordinates. When we manipulate our quadratic ax2 + bx + c, using 1 for a and b, and solve for c we find that c = –x2 – x

c function.JPG

Our xc plane appears to merely flip and shift our parent function, with our vertex at  


When we change our original value of c to 5, the red graph, or to .25, the black graph, our parabola dilates but also moves our vertex.

For the equation  our vertex lies at and the graph still has zeros at 0 and -1 which is reasonable


as our zeros are linked with our values of a and b and here we have not changed our a and b values.

For the equation  our zeros remain and our vertex lies at



If we animate the denominator for values between -10 and 10 we see the graph below.




You notice that the graph continues to have the original zeros and dilates while changing the vertex.

Also of interest is the point where c = 0 the graph is undefined.


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