How do you solve using the completing the square method $x^2 + 8x – 2 = 0$ ?

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How do you solve using the completing the square method $x^2 + 8x – 2 = 0$ ?

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Answer 1 · 2016-08-24T20:51:31

$x=-4-3sqrt2$ or $x=-4+3sqrt2$

Explanation:

Compare $x^2+8x-2=0$ with the identity $(x+a)^2=x^2+2ax+a^2$ . Note that to complete the square we have to add square of half of the coefficient of $x$ . As coefficient of x is 8 we should add and subtract $4^2$ . Hence,

$x^2+8x-2=0$ can be written as

$x^2+8x+16-16-2=0$ or

$(x+4)^2-18=0$ or

$(x+4)^2-(sqrt18)^2=0$ or

$(x+4)^2-(3sqrt2)^2=0$ or

$(x+4+3sqrt2)(x+4-3sqrt2)=0$ or

$x=-4-3sqrt2$ or $x=-4+3sqrt2$

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How do you solve using the completing the square method $x^2 + 8x – 2 = 0$ ?

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How do you solve using the completing the square method x^2 + 8x – 2 = 0x^2 + 8x – 2 = 0?

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How do you solve using the completing the square method $x^2 + 8x – 2 = 0$ ?