How do you solve using the completing the square method #x^2 + 4x = 7#?

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Answer 1 · 2016-02-26T19:36:53

See solution below.

#1(x^2 + 4x + m) = 7#

#m = (b/2)^2#

#m = (2)^2#

#m = 4#

#1(x^2 + 4x + 4) = 7#

Factor as a perfect square trinomial.

#1(x + 2)^2 = 7#

#(x + 2) = +-sqrt(7)#

#x = +-sqrt(7) - 2#

Don't forget the #+-# sign with the square root.

Practice exercises:

Solve for x by completing the square.

a) #3x^2 + 12x - 8 = 0#

b) #2x^2 + 7x + 15 = 0#

Good luck!