Adding 42 to a given positive number gives the same result as squaring the number….

Adding 42 to a given positive number gives the same result as squaring the number. Find the number

Correct Answer: Option C

Explanation

Let the given positive number be x
Then 4 + x = x²
0 = x² – x – 42
or x² – x – 42 = 0
x² – 7x + 6x – 42 = 0
x(x – 7) + 6(x – 7) = 0
= (x + 6)(x – 7) = 0
x = -6 or x = 7
Hence, x = 7