2 câu trả lời
$(2x-8)^8$
$=C^0_8.(2x)^8-C^1_8.(2x)^{8-1}.8+C^2_8.(2x)^{8-2}.(-8)^2-C^3_8.(2x)^{8-3}.8^3+C^4_8.(2x)^{8-4}.(-8)^4-C^5_8.(2x)^{8-5}.8^5+C^6_8.(2x)^{8-6}.(-8)^6-C^7_8.(2x)^{8-7}.8^7+C^8_8.(-8)^8$
$=256x^8-8192x^7+114688x^6-917504x^5+4587520x^4-14680064x^3+29360128x^2-33554432x+16777216$
Cách khai triển khác:
$(2x-8)^8$
$=\sum\limits_{k=0}^8C^k_8.(2x)^{8-k}.(-8)^k$
