IGCSE Maths Notes: Completing the Square and Solving Quadratic Equations
Completing the square make it possible to find the
maximum of minimum value of a quadratic function without sketching
it., or to solve quadratic equations without using the quadratic
formula.. We start with an expression
to
express in the form![]()
We might multip[ly this out to obtain
Now
we equate
to
this and solve for the coefficients a, b, c.
Example: Complete the square for the expression
![]()
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Equating coefficients of
![]()
Equating coefficients of
![]()
Equating constant terms:![]()
Hence
in
completed square form is![]()
Having completed the square we can solve the equation
![]()
![]()
Example: Complete the square for the expression
Hence
solve the equation
![]()
![]()
Equating coefficients of
![]()
Equating coefficients of
![]()
Equating constant terms:![]()
Hence
in
completed square form is![]()
Now we can solve
![]()
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