kevingretzky
use the quadratic formula to find any xintercepts on the graph of the equation.
y=x^2  8x 1
x=?



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mathsmind
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set y =0, and solve the quadratic equation

mathsmind
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\[x ^{2}8x1=0\]

ZeHanz
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Set a=1, b=8 and c=1 in the QF.

mathsmind
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\[x=4+\sqrt{17} or x=4\sqrt{17}\]

mathsmind
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yup exactly

mathsmind
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you need to use the quadratic formula

mathsmind
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\[x=\frac{ b \pm \sqrt{b^24ac} }{ 2a }\]

mathsmind
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so the final answer would be

mathsmind
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\[(4+\sqrt{17}, 0) and (4\sqrt{17}, 0)\]

kevingretzky
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8 square root 68 over 8?

mathsmind
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yup

kevingretzky
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is it over 4?

mathsmind
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if a =1 yes

kevingretzky
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so am i right? it is over 4

mathsmind
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over 2x1