How do you solve $x^2 - 30 = 8x$ by completing the square?

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Answer 1 · 2015-05-12T21:14:50

First subtract $8x$ from both sides to get $x^2 - 8x - 30 = 0$ .

$(x-4)^2 = x^2 - 8x + 16$

So:

$0 = x^2 - 8x - 30$

$= x^2 - 8x + 16 - 16 - 30$

$= (x-4)^2 - 46$

Add 46 to both sides to get

$(x-4)^2 = 46$

So we have

$x - 4 = +-sqrt(46)$

Add 4 to both sides to get

$x = 4 +-sqrt(46)$

How do you solve x^2 - 30 = 8xx^2 - 30 = 8x by completing the square?