Question

If a1= 7 and an = -4an-1 + n then find the value of a5

Answer 1

a₅ = 1701

Explanation:

`a_1=7\\\\a_n=-4a_(n-1) + n\\\\a_2 = -4*a_1 + 2\\\\`

= -4*7 + 2

= -28 + 2

= -26

a₃ = -4a₂ + 3

= -4*(-26) + 3

= 104 + 3

= 107

a₄ = -4a₃ + 4

= -4*107 + 4

= -428 + 4

= -424

a₅ = -4a₄ + 5

= -4*(-424) + 5

= 1696 + 5

= 1701