1/8+125x^3
1/2^3+5^3x^3 =(1/2+5x)((1/2)^2+1/2*5x +(5x)^2)
(1/2+5x)(1/4+5/2x+25x^2)
a^6/343 +8b^12/1000
a^6/7^3 +2^3b^12/10^3 =(a^2/7 +2b^4/10[(a^2/7)^2+a^2/7*2b^4/10+(2b^4/10)^2]
a^2/7+2b^4/10)(a^4/49+a^2b^4/35+4b^8/100)
1/27 +x^3/216
1/3^3+x^3/6^3 =(1/3+x/6)[(1/3)^2 +1/3*x/6 +(x/6)^2]
(1/3+x/6)(1/9+x/18+x^2/36)