Question

（x+1)(x+3)(x+5)(x+7)+15=0

Answer 1

（x+1)(x+3)(x+5)(x+7)+15=0，

(x^2+8x+7)(x^2+8x+15)+15=0,

令x^2+8x+11=t,方程成为

(t-4)(t+4)+15=0,

t^2=1,

t=±1.

(1).t=-1时，

x^2+8x+11=-1,x^2+8x+12=0,

x1=-2,x2=-6,

(2).t=1时，

x^2+8x+11=1,x^2+8x+10=0,

x3=-4+√6,x4=-4-√6.