Answer:
Step-by-step explanation:
let side of cube=x cm
volume=x³ cm³
again side=(x-3) cm
volume=(x-3)³ cm³
x³-(x-3)³=1385
(a³-b³)=(a-b)(a²+ab+b²)
(x-x+3){x²+x(x-3)+(x-3)²}=1385
3(x^2+x²-3x+x²-6x+9)=1385
3(3x²-9x+9)=1385
9x²-27x+27=1385
9x²-27x+27-1385=0
9x²-27x-1358=0
[tex]x=\frac{27\pm\sqrt{(-27)^2-4*9*(-1358)} }{2*9} \\x=\frac{27\pm\sqrt{729+48888} }{18} \\or~x=\frac{27\pm\sqrt{49617} }{18} \\or~x=\frac{27\pm 222.749}{18} \\taking positive side only as negative sign gives negative length.\\or~x=\frac{27+222.749}{18} \\or~x\approx13.87[/tex]
