Respuesta :
Answer:
x = - 3, x = 6
Step-by-step explanation:
x² - 3x - 18 = 0 ( add 18 to both sides )
x² - 3x = 18
To complete the square
add ( half the coefficient of the x- term )² to both sides
x² + 2(- [tex]\frac{3}{2}[/tex] )x + [tex]\frac{9}{4}[/tex] = 18 + [tex]\frac{9}{4}[/tex]
(x - [tex]\frac{3}{2}[/tex] )² = [tex]\frac{81}{4}[/tex] ( take square root of both sides )
x - [tex]\frac{3}{2}[/tex] = ± [tex]\sqrt{\frac{81}{4} }[/tex] = ± [tex]\frac{9}{2}[/tex] ( add [tex]\frac{3}{2}[/tex] to both sides )
x = [tex]\frac{3}{2}[/tex] ± [tex]\frac{9}{2}[/tex]
Then
x = [tex]\frac{3}{2}[/tex] - [tex]\frac{9}{2}[/tex] = [tex]\frac{-6}{2}[/tex] = - 3
x = [tex]\frac{3}{2}[/tex] + [tex]\frac{12}{2}[/tex] = 6
