Completing the square?

2 ⤊

Completing the square?

x^2+8x+5=0

thanks!

2007-10-02 22:37:03 · 3 answers · asked by K Rose 3 in Science & Mathematics ➔ Mathematics

3 answers

x^2 + 8x + 5 = 0
x^2 + 8x + 4^2 - 4 ^2 = -5

since (a+b)^2 = a^2 + 2ab + b^2,

(x + 4)^2 - 4^2 = -5
(x + 4)^2 = -5 + 16
(x + 4)^2 = 11
x + 4 = +/- sqrt(11)
x = -4 +/- sqrt(11)

2007-10-02 22:53:12 · answer #1 · answered by Davis 1 · 0⤊ 0⤋

x^2+8x+5=0
x^2 + 8x = -5
x^2 + 8x + 16 = -5 + 16
(x + 4)^2 = 11
(x + 4) = 11 or (x + 4) = -11
x = -15 or x = 7

2007-10-02 23:23:36 · answer #2 · answered by ♪£yricảl♪ 4 · 0⤊ 1⤋

( x Â² + 8 x + 16 ) + 5 = 16
( x + 4 ) Â² = 11
( x + 4 ) = Â± â11
x = - 4 Â± â11

2007-10-03 05:04:52 · answer #3 · answered by Como 7 · 2⤊ 1⤋