Question

(x+3) x (x+1) = 21
Alguém me ajuda

Answer 1

Resposta:

(x + 3) . (x + 1) = 21

$x^{2}$ + 4x + 3 = 21

$x^{2}$ + 4x + 3 - 21 = 21 - 21

$x^{2}$ + 4x + 3 - 21 = 0

$x^{2}$ + 4x - 18 = 0

$x^{2}$ + 4x - 18 = 0

a = 1,   b = 4,   c = -18

Δ = $b^{2}$ - 4ac

Δ = $4^{2}$ - 4 . 1 . (-18)

Δ = 16 + 72

Δ = 88

$\frac{-b +- \sqrt{Delta} }{2a}$

$x_{1}$ = $\frac{-4 + \sqrt{88} }{2.1}$ = $\frac{-4 + 9.38083151965}{2}$ = 2.69041575983

$x_{2}$ =  $\frac{-4 - \sqrt{88} }{2.1}$ = $\frac{-4 - 9.38083151965}{2}$ = -6.69041575985