Question

me ajude a número nove por favor

Answer 1

x + $x^{2}$ = 90 
$x^{2} + x - 90= 0$
Δ= $b^{2} - 4.a.c$
a = 1 b = 1 c = -90
Δ = $1^{2}$ - 4.1.-90
Δ = 1 + 360
Δ = 361

x = -b +- $\sqrt{Δ}$ / 2a
x = $\frac{-1 +- 19}{2.1}$
$x¹= \frac{-1-19}{2} = \frac{-20}{2} = -10$
$x²= \frac{-1+19}{2}= \frac{18}{2} = 9$

-10 ou 9