Question

Please give answers
Sum of first n term is 4n- n2 find the first term and find sum of first two term and also find 3rd and n term?

Answer 1

Answer:

Step-by-step explanation:

Answer 2

HEY MATE.....!
HERE'S THE ANSWER.....

Given:

sum of 1st n terms = $(4n - {n}^{2} )$

We know that:

sum of 1st n terms = $\frac{n}{2} {2a + (n - 1)d}$

=> $\frac{n}{2} {2a + (n - 1)d} \: = \: 4n - {n}^{2}$

=> $\frac{n}{2} {2a + (n - 1)d} \: = \: n(4 - n)$

=> $\frac{1}{2} \: {2a + (n - 1)d} \: = \: (4 - n)$

=> ${2a + (n - 1)d} \: = \: 2(4 - n)$

=> ${2a + (n - 1)d} \: = \: 8 - 2n$

=> ${2a + dn - d} = 8 - 2n$

Hey dear, Solve this equation and you will get the answer.....