The distance covered by a train in $(5 y-1)$ hours is $\left(125 y^3-1\right)$ km. The speed of the train is:
Answer & explanation
Correct answer: option 4
Distance = Speed × Time
Speed =\(\frac{125y^3 - 1 }{(5y - 1)}\)
By using formula :-
a^3 - b^3 = (a-b) ( a^2 + b^2 + ab)
Speed = ( 25y^2 + 5y + 1 ) km/h