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The points $(3,8)$ and $(5,2)$ lie at the ends of a diameter of a circle. What is the equation of the circle?
In the previous question, two points were enough to specify a circle. But is that always the case? For each of the following three statements, is the answer ALWAYS, SOMETIMES or NEVER? Do justify your answers!
You might like to explore your ideas with Geogebra.
We now know that given three distinct points in the plane, there is (usually) a unique circle passing through them.
So if we are given three points, we would like to find the equation of the circle that passes through them. How many ways can you find to do this?
Here are some examples for you to try your ideas out on. For each set of three points, find the equation of the circle passing through them.
It is certainly worth sketching a graph to help you understand what is going on in each case!
Which of your approaches is the most effective?
This comes in two parts, with the first being less fiendish than the second. It’s great for practising both quadratics and laws of indices, and you can get a lot from making sure that you find all the solutions. For a real challenge (requiring a bit more knowledge), you could consider finding the complex solutions.
You're invited to decide whether statements about the number of solutions of a quadratic equation are always, sometimes or never true.
This will encourage you to think about whether all quadratics can be factorised and to develop a better understanding of the effect that changing the coefficients has on the factorised form.