F4quatratic equation

x (x + 2) (x + 4) (x + 6) - 21 = 0x(x + 6) (x + 2)(x + 4) - 21 = 0(x² + 6x) (x² + 6x + 8) - 21 = 0(x² + 6x + 4 - 4) (x² + 6x + 4 + 4) - 21 = 0(x² + 6x + 4)² - 4² - 21 = 0(x² + 6x + 4)² - 37 = 0(x² + 6x + 4 - √37) (x² + 6x + 4 + √37) = 0(x² + 6x + 4 - √37) = 0 or (x² + 6x + 4 + √37) = 0x = ( - 6 ± √ (6² - 4(4 - √37)) ) / 2 or x = ( - 6 ± √ (6² - 4(4 + √37)) ) / 2 x = - 3 ± √ (5 + √37) or x = - 3 ± √ (5 - √37) = - 3 ± i √ (√37 - 5)

2011-10-20 19:08:31 補充：
Chak Pui( 小學級 4 級 )

你即管抄吧,你很想被檢舉吧?

x (x + 2) (x + 4) (x + 6) - 21 = 0x(x + 6) (x + 2)(x + 4) - 21 = 0(x² + 6x) (x² + 6x + 8) - 21 = 0(x² + 6x + 4 - 4) (x² + 6x + 4 + 4) - 21 = 0(x² + 6x + 4)² - 4² - 21 = 0(x² + 6x + 4)² - 37 = 0(x² + 6x + 4 - √37) (x² + 6x + 4 + √37) = 0(x² + 6x + 4 - √37) = 0 or (x² + 6x + 4 + √37) = 0x = ( - 6 ± √ (6² - 4(4 - √37)) ) / 2 or x = ( - 6 ± √ (6² - 4(4 + √37)) ) / 2
x = - 3 ± i √ (√37 - 5) or - 3 ± √ (5 + √37)