Question

Calcule -5x^2 + 40x - 75

Answer 1

-5x² + 40x - 75 = 0

a = -5; b = 40; c = -75

x = [- b ± √(b² - 4ac)] / 2a
x = [- 40 ± √(40² - 4 . [-5] . [-75])] / 2 . (-5)
x = [- 40 ± √(1600 - 1500)] / -10
x = [- 40 ± √100] / -10
x = [- 40 ± 10] / -10 
x' = [- 40 + 10] / -10 = -30 / -10 = 3
x'' = [- 40 - 10] / -2 = -50 / -10 = 5

S = {3, 5}

Espero ter ajudado. Valeu!