Question

if n(n-1) = 90, then find the value of n. with details please.​

Answer 1

Step-by-step explanation:

Solution:

n

P

2

=90

or,

(n−2)!

n!

=90

or, n(n−1)=90

or, n

2

−n−90=0

or, n

2

−10n+9n−90=0

or, n(n−10)+9(n−10)=0

or, (n−10)(n+9)=0

or, n=10 or =n=−9

n can't be negative so, n=10.