O Level Maths Notes: The Quadratic Formula



A quadratic equation is an equation of the formwhere We can solve equations of this form by identifying a, b and c and substituting them into the formula

to find

Example:
Solve




Then or



It is very important to get the correct values ofFor the following equations the values are given

Notice that if a minus sign appears in the formula we have to solve then that value of will be negative.

Then for the first equation

We may also solve quadratic equations by sketching a quadratic graph or by completing the square.

Example:Solve

Thenor



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