2021 · Q19
If the roots of the equation x² − 4x − log₁₀N = 0 are real, then what is the minimum value of N ?
Elementary MathematicsAlgebra
- A0.1
- B0.01
- C0.001
- D0.0001
Explanation
Real roots require Δ = 16 + 4log₁₀N ≥ 0, i.e. log₁₀N ≥ −4. The logarithm is increasing, so N ≥ 10⁻⁴ = 0.0001. The minimum value of N is therefore 0.0001, option (d).