High School Maths Examples and Questions

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Solving quadratics of the form x2 + bx + c = 0 by factorising first

This means find the values of x where the quadratic x2 + bx + c = 0 This can be done as follows:

 i. Factorise x2 + bx + c = 0 into the form (x + n)(x + q)
This has already been shown in Factorising Quadratics − 1
 ii. So (x + n)(x + q) = 0
 iii. The values in either of the above brackets must equal to 0, as brackets means multiply and anything multipled by 0 is equal to 0. So:
       x + n = 0  =>  x = −n  or
       x + q = 0  =>  x = −q   

Remember:
Find the values of x where x2 + bx + c = 0 is the same as solve x2 + bx + c = 0


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