Question

x ao quadrado-10x+9=0

Answer 1

x²-10x-9=0
x²-10x=-9
x(x-10)= -9 
x=-9 ou x=1

Answer 2

x² - 10x + 9 = 0
a = 1, b = -10, c = 9
Δ = b² - 4ac
Δ = (-10)² - 4.1.9
Δ = 100 - 36
Δ = 64
x = (-b+/-√Δ)/2a
x = [-(-10)+/-√64]/2.1
x = (10+/-8)/2
x' = (10+8)/2 = 18/2 = 9
x" = (10-8)/2 = 2/2 = 1
S: {1; 9}