初二数学题,分解因式(x+1)(x+3)(x+5)(x+7)+16,快点啦

xxxx+16xxx+86xx+176x+121

(x^2+8x+7)(x^2+8x+15)+16=(x^2+8x)^2+22(x^2+8x)+121=(x^2+8x+11)^2

=[(x+1)(x+7)][(x+3)(x+5)]+16
=[(x²+8x)+7][(x²+8x)+15]+16
=(x²+8x)²+22(x²+8x)+105+16
=(x²+8x)²+22(x²+8x)+121
=[(x²+8x)+11]²
=(x²+8x+11)²