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

Question

1294 views around the world

You can reuse this answer
Creative Commons License

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!

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