Verified answer

x = [-(-5) ± √((-5)^2 - 4(1)(9)]/(2 • 1) = [5 ± √(25 - 36)]/2 = (5 ± i√11)/2

x = [ -b ±√(b² - 4ac)]/(2a) works for equations in the form of ax² + bx + c = 0 ( note x² is written as x^2 when you don't have access to superscript as x2 = 2x)

so in the case of x² - 5x + 9 = 0

a = 1, b = -5, and c = 0

=> x = [ -(-5) ±√((-5)² - 4*1*9)]/(2*1)

=> x = [ 5 ±√(25 - 36)]/2

=> x = [ 5 ±√(-1 * 11)]/2

=> x = (5 ±i√11)/2

=> x = (5 -i√11)/2 and (5+i√11)/2

x²+5x + 4 = 0 Use the quadratic formula to sparkling up    ax²+bx+c=0 the place    a=a million    b=5    c=4 x = [-b ± ?(b²-4ac)] / (2a)    = [-(5) ± ?((5)² - 4(a million)(4))] / (2·a million)    = [-5 ± ?(9)] / 2    = [-5 ± 3] / 2    = -2.5 ± a million.5    = -4, -a million

x^2 -5x = -9

ADD 25/4

x^2 -5x +25/4 = -9 +25/4

( x - 5/2)^2 = -11/4

x = 1/2 ( 5 + i \/11 ) OR 1/2 ( 5 - i \/11 ) ANSWER

{x = 1/2 (5 - i Sqrt[11])}, {x = 1/2 (5 + i Sqrt[11])}

x = [- b ± √ (b² - 4ac ] / (2a)

x = [ 5 ± √ (25 - 36) ] / 2

x = [ 5 ± i √ 11 ] / 2