We have, $a_n$ = $(-1)^{n-1} 5^{n+1}$ Substituting n = 1, 2, 3, 4, 5, we get $a_1$ = $(-1)^{1-1} 5^{1+1}$ = $(-1)^0 5^2$ = 25 , $a_2$ = $(-1)^{2-1} 5^{2+1}$ = $(-1)^1 5^3$ = - 125 $a_3$ = $(-)^{3-1} 5^{3+1}$ = $(-1)^2 5^4$ = 625, $a_4$ = $(-1)^{4-1} 5^{+1}$ = $(-1)^3 5^3$ = - 3125 $a_5$ = $(-1)^{5-1} 5^{5+1}$ = $(-1)^4 5^6$ = 15625 ∴ The first five terms are 25, – 125, 625, –3125, 15625.