zxl2945
BunuelThere are discussions about Z taking the value 1, 1/2
Could you please kindly explain why can't Z take the value 0?
Thank you
How many values of Z satisfy \((|2Z|)! – |Z| = Z\) ?A. 0
B. 1
C. 2
D. 3
E. More than 3
Let's check two cases for \((|2z|)! - |z| = z\)
If \(z < 0\), then we'd have:
\((-2z)! - (-z) = z\)
\((-2z)! = 0\)
Since the factorial of none of the numbers equals 0, then this equation has no solution. Thus, \((|2z|)! - |z| = z\) does not have a solution when \(z < 0\).
If \(z ≥ 0\), then we'd have:
\((2z)! - z = z\)
\((2z)! = 2z\)
For integer
n, \(n! = n\) only in two cases: when \(n = 1\) and when \(n = 2\), in all other cases \(n! > n\). Thus, either \(2z = 1\) or \(2z = 2\). Therefore, \(z = \frac{1}{2}\) or \(z = 1\).
Answer: C.
P.S. z cannot be 0 because this value does not satisfy \((|2z|)! - |z| = z\). If \(z = 0\), we get:
\((|0|)! - |0| = 0\)
\(0! - 0 = 0\)
\(1 - 0 = 0\) (recall that \(0! = 1\))
\(1 = 0\)
Which is not true.