f.4,,如果sum of real roots 係-2,,product of 係-3,,錦quad. for.係?!

quadratic formula is x^2 + 2x - 3 = 0

因sum of real roots 係 -b / a
所以代入去時, b 會轉o左係 +2

而product of roots 係 c / a
所以代入就唔駛轉正負數

正確的是這樣的, x^2 - (sum of real roots)x + (product of real roots) = 0