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Rearrange expressions in the form $ax^2+bx+c$ to $a(x+b)^2+c$.

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We can rewrite quadratic equations given in the form $ax^2+bx+c$ as a square plus another term - this is called \"completing the square\".

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This can be useful when it isn't obvious how to fully factorise a quadratic equation.

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Rewrite the following expressions in the form \\[(x+b)^2-c\\]

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Completing the square works by noticing that

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\\[ (x+a)^2 = x^2 + 2ax + a^2 \\]

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So when we see an expression of the form $x^2 + 2ax$, we can rewrite it as $(x+a)^2-a^2$.

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Replace $x^2+\\var{evens2}x$ with $(x+\\var{evens2/2})^2 - \\var{evens2/2}^2$. Remember to keep the $\\var{evens2-evens1}$ term on the end!

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\\begin{align}
\\simplify[basic]{ x^2 + {evens2}x + {evens2-evens1}}  &= \\simplify[basic]{ (x+{evens2/2})^2 - {evens2/2}^2 + {evens2-evens1} } \\\\
&= \\simplify[basic]{ (x+{evens2/2})^2 + {evens2-evens1 - evens2^2/4} }
\\end{align}

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Use this link to find some resources which will help you revise this topic.

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$\\simplify {x^2+ {evens2}x +{evens2-evens1}} =$ [[0]]

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It doesn't look like you've completed the square.

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