m2 – 84 = 0

(v). m² – 84 = 0

Sol. m² – 84 = 0

∴ m² = 84

∴ m = ±√84

∴ m = ±√(2× 2× 3× 7)

∴ m = ±2√(3× 7)

∴ m = ± 2√21

∴ m = 2√21  or – 2√21