Question

The product of two consecutive room numbers is 420. find the room numbers.

Answer 1

hello :
the consecutive room numbers are : n , n+1
n(n+1) =420
n²+n -420 = 0
the discriminant delta = b² - 4ac ( a = 1 and b = 1 and c = - 420
delta = (1)²-4(1)(-420) =1681= 41²
n = (-1 -41)/2 ( refused negatif number)
or
n = (-1+41)/2 =20
the room numbers.are : 20 , 21

Answer 2

Explanation:

Let the first number is x and other number is (x+1). The product of two consecutive room numbers is 420.

So, according to question,

`x* (x+1)=420`

`x^2+x-420=0`

On solving the above quadratic equation, we get the value of x as:

x = 20

and

(x+1) = 21

So, two numbers are 20 and 21.