Answer:
Step-by-step explanation:
ax² + bx + c = a(x - [tex]x_{1}[/tex])(x - [tex]x_{2}[/tex])
D = b² - 4ac
[tex]x_{12}[/tex] = ( - b ± √D ) / 2a
~~~~~~~~~~~~
Let x² = y , then y² + 8y - 9
Find the roots of equation y² + 8y - 9 = 0
D = 64 + 36 = 100 = 10²
[tex]y_{1}[/tex] = ( - 8 - 10) / 2 = - 9
[tex]y_{2}[/tex] = ( - 8 + 10) / 2 = 1
y² + 8y - 9 = (y - 1)(y + 9) = (x² - 1)(x² + 9)
x² = 1 ⇒ [tex]x_{12}[/tex] = ± √1
[tex]x^{4}[/tex] + 8x² - 9 = (x - 1)(x + 1)(x² + 9)
