Adding 42 to a given positive number gives the same result as squaring the number. Find the number
A
14
B
13
C
7
D
6
Verified Correct Answer: C.
Step-by-Step Mathematical Solution
Let the given positive number be x
Then x + 42 = \(x^2\)
0 = \(x^2\) - x - 42
or \(x^2\) - x - 42 = 0
\(x^2\) - 7x + 6x - 42 = 0
x(x - 7) + 6(x - 7) = 0
= (x + 6)(x - 7) = 0
x = -6 or x = 7
Hence, x = 7
Source: Myschool Past Questions Archive (Record #45711)