Solve x^2+8x-5 = 0 by completing the square.
x2 + 8x = (x + 4)2 - 16, so x2 + 8x - 5 = (x + 4)2 - 16 - 5 = (x + 4)2 - 21, so then (x + 4)2 - 21 = 0 (x + 4)2 = 21 -----> x + 4 = √21 -------> x = -4 + √21 x = -4 - √21
SJ
x2 + 8x = (x + 4)2 - 16, so x2 + 8x - 5 = (x + 4)2 - 16 - 5 = (x + 4)2 - 21, so then (x + 4)2 - 21 = 0 (x + 4)2 = 21 -----> x + 4 = √21 -------> x = -4 + √21 x = -4 - √21
