Question

√x=7-x com q resolve isso??

Answer 1

√x=7-x

x = (7-x)²

x = 7² - 2 . 7 . x + x²

x= 14 - 14x + x²

x² - 14x - x + 14 = 0

x² -15x + 14 = 0

Δ=b²-4ac

Δ=15² - 4 . 1 . 14

Δ=225-56

Δ=169

x=(-b+-√Δ)/2a

x=[-(-15)+-√169]/2

x=(15+-13)/2

x'=(15-13)/2 => 2/2 = >2

x"=(15+13)/2 => 28/2 =>14

S={2, 14}