How do you solve $x^2 + 2x-7=0$ by completing the square?

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Answer 1 · 2015-04-29T19:59:37

Move the constant term to the right side of the equation, then add whatever quantity is necessary to both sides so the left side is a square

$x^2+2x - 7 = 0$

$x^2+2x = 7$

If the first two terms of $(x+a)^2 = x^2 +2ax +a^2$
are $x^2 and 2x$
then $a=1$

$x^2+2x+1 = 7+1$

$(x+1)^2 = 8$

$x+1 = +-sqrt(8)$

$x = -1+-2sqrt(2)$

How do you solve x^2 + 2x-7=0x^2 + 2x-7=0 by completing the square?