Question 1102340
Simple way:
{{{x^2-6x+5}}}
{{{(x-1)(x-5)}}}
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{{{(1+5)/2=6/2=3}}}
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{{{f(3)=3^2-6*3+5}}}
{{{9-18+5}}}
{{{-4}}}

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VERTEX (3,-4)

SYMMETRY AXIS x=3