2015 · Q25
If the roots of the quadratic equation x² - 4x - ₁0} N = 0 are all real then the minimum value of N is
Elementary MathematicsTime, Speed and Distance
- A1/100
- B1/1000
- C1/10000
- D10000
Explanation
Real roots need discriminant 16 + 4*log10(N) >= 0, i.e. log10(N) >= -4, so N >= 10^(-4) = 1/10000. Hence option (c).