Question

a positive number when decreased by 4 is equal to 21 times of the reciprocal of the number find that number

Answer 1

Let the number be x.

Given, x - 4 = 21/x

            x^2 - 4x - 21 = 0

           (x-7)(x+3) = 0

           x = 7 and x = -3. 

Since the number cannot be negative.

x = 7.


Hope this helps!

Answer 2

Answer:

7

Step-by-step explanation:

Let the number be x

reciprocal of number = 1/x

Since we are given that a positive number when decreased by 4 is equal to 21 times of the reciprocal of the number

x-4 = 21(1/x)

x^2-4x-21=0

x^2-7x+3x-21=0

x(x-7)+3(x-7)=0

(x+3)(x-7)=0

So, x = -3,7

Since we are given that the number is positive

So, the number is 7