Question

x(x-4)=(4-x)(4+x)
A=1
B=1
C=-4

Answer 1

resolvendo:
x²-4x=16+4x-4x-x²
2x²-4x-16=0

agora por baskara:
a=2 b=-4 c=-16
Δ=b²-4ac
Δ=(-4)²-4.2.(-16)
Δ=16+128
Δ=144

x=(-b+-√Δ)/2a
x=(4+-12)/4
x'=(4+12)/4=16/4=4
x"=(4-12)/4=-8/4=-2