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)#