Question

1 + 4 + 7 + .... + (3n - 2) = n(3n - 1)/2

Answer 1

Answer:

let unknown number be n

1+4+7+n+(3n-2)=n(3n-1)/2

12+n+3n-2=3n-n/2

12+4n=2n/2

12*2=2n-4n

24= -2n

24/-2= n

-12=n

Answer 2

Step-by-step explanation:

let a no. n

1

$+ 4 + 7 + n + (3n - 2) = n(3n - 1) \div 2$

solve this