Question

Como faz essa conta x⁴-8x²=-15

Answer 1

x^4 - 8x² + 15 = 0
x² = y --> x = +/-\/y
x^4 = (x²)² = y²

y² - 8y + 15 = 0
/\ = (-8)² - 4.1.15
/\ = 64 - 60
/\ = 4
y = [-(-8)+/-\/(4)]/2.1
y = (8+/-2)/2
y' = (8+2)/2 = 10/2 = 5 --> x' = +/-\/5
y" = (8-2)/2 = 6/2 = 3 --> x = +/-\/3
S: (-\/5, -\/3, \/3, \/5)