How do you solve $x^2 - 6x = 391$ by completing the square?

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How do you solve $x^2 - 6x = 391$ by completing the square?

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Answer 1 · 2016-04-12T07:29:39

$x=23$ or $x-17$

Explanation:

In $x^2-6x=391$ as the Left Hand Side is $x^2-6x$ , we can make it a complete square (compare it with $(x-a)^2=x^2-2ax+a^2$ ) by adding **square of half the coefficient of $x$ .

As coefficient of $x$ is $-6$ , we need to add $(-6/2)^2=9$ , to each side and then we have

$x^2-6x+9=391+9=400$

or $(x-3)^2=20^2$

Hence either $x-3=20$ or $x-3=-20$ i.e.

$x=23$ or $x-17$

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How do you solve $x^2 - 6x = 391$ by completing the square?

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Science

Math

Humanities

... and beyond

How do you solve x^2 - 6x = 391x^2 - 6x = 391 by completing the square?

1 Answer

Explanation:

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How do you solve $x^2 - 6x = 391$ by completing the square?