（a+b)的1到9次方都写出来（a-b)的1到9次方都写出来就直接写出来

Question

（a+b) 的1到9次方都写出来
（a-b)的1到9次方都写出来
就直接写出来

Answer 1

（a+b)^1=a+b,
（a+b)^2=a^2+2ab+b^2,
（a+b)^3=a^3+3a^2b+3ab^2+b^3,
（a+b)^4=a^4+4a^3b+6a^2b^2+4ab^3+b^4
（a+b)^5=a^5+5a^4b+10a^3b^2+10a^2b^3+5ab^4+b^5
（a+b)^6=a^6+6a^5b+15a^4b^2+20a^3b^3+15a^2b^4+6ab^5+b^6
（a+b)^7=a^7+7a^6b+21a^5b^2+35a^4b^3+35a^3b^4+21a^2b^5+7ab^6+b^7
（a+b)^8=a^8+8a^7b+28a^6b^2+56a^5b^3+70a^4b^4+56a^3b^5+28a^2b^6+8ab^7+b^8
（a+b)^9=a^9+9a^8b+36a^7b^2+84a^6b^3+126a^5b^4+126a^4b^5+84a^3b^6+36a^2b^7+9ab^8
+b^9
（a-b)的1到9次方可以看成【a+(-b)】的1到9次方,上面的等式中,凡是出现有b^(2n-1),即b,b^3,b^5,b7,b^9,此项前面的+改为-,即：
（a-b)^1=a-b,
（a-b)^2=a^2-2ab+b^2,
（a-b)^3=a^3-3a^2b+3ab^2-b^3,
（a-b)^4=a^4-4a^3b+6a^2b^2-4ab^3+b^4
（a-b)^5=a^5-5a^4b+10a^3b^2-10a^2b^3+5ab^4-b^5
（a-b)^6=a^6-6a^5b+15a^4b^2-20a^3b^3+15a^2b^4-6ab^5+b^6
（a-b)^7=a^7-7a^6b+21a^5b^2-35a^4b^3+35a^3b^4-21a^2b^5+7ab^6-b^7
（a-b)^8=a^8-8a^7b+28a^6b^2-56a^5b^3+70a^4b^4-56a^3b^5+28a^2b^6-8ab^7+b^8
（a-b)^9=a^9-9a^8b+36a^7b^2-84a^6b^3+126a^5b^4-126a^4b^5+84a^3b^6-36a^2b^7+9ab^8
-b^9