Yes but the turning point of a negative quadratic is also it's maximum as squares of real numbers have a minimum of zero. Other functions don't have simple algebraic properties like this that allow you to find their maxima and minima, which is why you learn new techniques at A-Level
For the 1st question, why did you complete the square? (Isn't that just for finding the turning point).
Yes but the turning point of a negative quadratic is also it's maximum as squares of real numbers have a minimum of zero.
Other functions don't have simple algebraic properties like this that allow you to find their maxima and minima, which is why you learn new techniques at A-Level