Explanation:
Assuming you mean 2x² + 8x − 1 = 0, this equation isn't factorable, so use quadratic formula.
x = [ -b ± √(b² − 4ac) ] / 2a
x = [ -8 ± √(8² − 4(2)(-1)) ] / 2(2)
x = [ -8 ± √(64 + 8) ] / 4
x = (-8 ± √72) / 4
x = (-8 ± 6√2) / 4
x = (-4 ± 3√2) / 2