(a+b)^6=a^6+6a^5b+15a^4b^2+20a^2b^3+15a^2b^4+6ab^5+b^6 (a-b)^5=a^5-5a^4b+10a^3b^2-10a^2b^3+5ab^4-b^5 (a+2b)^4=a^4+8a^3b+24a^2b^2+32ab^3+16b^4
