Question

n(n-1) =210then find the value of n

Answer 1

Hi ,

n ( n - 1 ) = 210

n ( n - 1 ) = 15 × 14

n ( n - 1 ) = 15 ( 15 - 1 )

Compare both sides ,

we conclude that ,

n = 15

or

n ( n - 1 ) = ( -14 ) [ - 14 - 1 ]

n = -14

Therefore ,

n = 15 or - 14

second method :

n ( n - 1 ) = 210

n² - n - 210 = 0

n² - 15n + 14n - 210 = 0

n ( n - 15 ) + 14( n - 15 ) = 0

( n - 15 ) ( n + 14 ) = 0

n - 15 = 0 or n + 14 = 0

n = 15 or n = - 14



I hope this helps you.

:)