Question

25 x ao quadrado igual a 20 x menos 4

Answer 1

25x² = 20x - 4
25x² - 20x + 4 = 0 

a = 25
b = - 20
c = 4

Δ = b² -4 .a . c
Δ = (-20)² -4 . 25 . (4)
Δ = 400 - 100 . 4
Δ = 400 - 400
Δ = 0

Δ = 0, existe duas solução iguais. "uma raiz".

$\mathtt{\dfrac{-b+-~\sqrt{\Delta}}{2~.~a}~~=~~\dfrac{-(-20)+-~\sqrt{0}}{2~.~25}~~=~~\dfrac{20+-~0}{50}} \\ \\ \\ \mathtt{x' = \dfrac{20+0}{50}~~=~~\dfrac{20}{50}~~=~~\drac{2}{5}} \\ \\ \\ \mathtt{x'' = \dfrac{20-0}{50}~~=~~\dfrac{20}{50}~~=~~\dfrac{2}{5}} \\ \\ \\ \boxed{\boxed{\mathtt{Resposta: S = \dfrac{2}{5}}}}$