To find natural numbers if four consecutive natural numbers are multiple of 5 and product is 15000

Question

The product of four consecutive natural number which are multiple of 5 is 15000.Find the natural numbers

Answer 1

x * (x + 5) * (x + 10) * (x + 15) = 15000

x^4 + 30 x^3 + 275 x^2 + 750 x = 15000

x^4 + 30 x^3 + 275 x^2 + 750 x - 15000 = 0

The roots are x = 5, x = -20, x = -15/2 + (5/2)(sqrt(15))i, and x =  -15/2 - (5/2)(sqrt(15))i

The only natural number (non-negative integer) solution is x = 5, so:

The answer is 5, 10, 15, 20.