Question

O número 8 é raiz da equação X ELEVADO A 2 + 9 X - 18 = 0
V ou F?

Answer 1

x² + 9x - 18 = 0
a = 1; b = 9; c = - 18

Δ = b² - 4ac
Δ = 9² - 4.1.(-18)
Δ = 81 + 4.18
Δ = 81 + 72
Δ = 153
Δ = 9.51
√Δ = √9.√17
√Δ = 3.√17

x = - b +/- √Δ = - 9 +/- 3√17
          2a                 2.1

x' = - 9 + 3√17
             2

x" = - 9 - 3√17
           2
-----------------------------------------
153: 3
51: 3
17: 17
1

Answer 2

$x^{2} +9x-18=0\\\\ a=1;~b=9;~c=-18\\\\\\ \Delta=b^2-4ac\to \Delta=9^2-4.1.(-18)\to \Delta=81+72\to \boxed{\Delta=153}\\\\ x' \neq x'' \\\\\\x= \dfrac{-b\pm \sqrt{\Delta} }{2a} \to~~ x= \dfrac{-9\pm \sqrt{153} }{2.1} \to~~ x= \dfrac{-9\pm 3\sqrt{17} }{2} \to\\\\\\ \boxed{x'= \dfrac{-9+ 3\sqrt{17} }{2}} \\\\\\ \boxed{x''= \dfrac{-9-3\sqrt{17} }{2}}\\\\\\\\\\ \large\boxed{\boxed{ \dfrac{-9+ 3\sqrt{17} }{2}~;~\dfrac{-9-3\sqrt{17} }{2} } }$



R.: 8 não é raiz dessa equação.