Question

x ao quadrado -8+16=0

Answer 1

x²-8+16=0
x²=0+8-16
x²=-8

Answer 2

x² - 8x + 16 = 0
a = 1; b =  - 8; c = 16
Δ = b² - 4ac
Δ = (-8)² - 4.1.16
Δ = 64 - 64
Δ = 0

x = - b +/- √Δ   = - (-8) +/- √0
      --------------    ------------------ 
             2a               2.1

x = 8/2
x = 4