Question

A positive number when decresed by 4 is equal to 21 times the reciprocal of the number is
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Answer 1

Let number = x  

Since, number is positive number, therefore, x > 0

Number decreased by 4 = x - 4

Reciprocal of number = 1/x

Therefore, x - 4 = 21 * (1/x)

=> x(x - 4) = 21 => x^2 - 4x = 21

=> x^2 - 4x - 21 = 0 => x^2 + 3x - 7x - 21 = 0

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

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

=> x + 3 = 0 or x - 7 = 0

=> x = -3 or x = 7

Since, x > 0, therefore, x = 7

Hence, the number is 7

Answer 2

Answer:

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