解答
展开 (x+a)3(x+b)5
解答
x8+5x7b+10x6b2+10x5b3+5x4b4+x3b5+3ax7+15ax6b+30ax5b2+30ax4b3+15ax3b4+3ax2b5+3x6a2+15x5a2b+30x4a2b2+30x3a2b3+15x2a2b4+3xa2b5+a3x5+5a3x4b+10a3b2x3+10a3b3x2+5xa3b4+a3b5
求解步骤
(x+a)3(x+b)5
展开 (x+a)3:x3+3ax2+3xa2+a3
=(x3+3ax2+3xa2+a3)(x+b)5
=(x+b)5(x3+3ax2+3xa2+a3)
打开括号=(x+b)5x3+(x+b)5⋅3ax2+(x+b)5⋅3xa2+(x+b)5a3
=x3(x+b)5+3ax2(x+b)5+3xa2(x+b)5+a3(x+b)5
展开 x3(x+b)5:x8+5x7b+10x6b2+10x5b3+5x4b4+x3b5
=x8+5x7b+10x6b2+10x5b3+5x4b4+x3b5+3ax2(x+b)5+3xa2(x+b)5+a3(x+b)5
展开 3ax2(x+b)5:3ax7+15ax6b+30ax5b2+30ax4b3+15ax3b4+3ax2b5
=x8+5x7b+10x6b2+10x5b3+5x4b4+x3b5+3ax7+15ax6b+30ax5b2+30ax4b3+15ax3b4+3ax2b5+3xa2(x+b)5+a3(x+b)5
展开 3xa2(x+b)5:3x6a2+15x5a2b+30x4a2b2+30x3a2b3+15x2a2b4+3xa2b5
=x8+5x7b+10x6b2+10x5b3+5x4b4+x3b5+3ax7+15ax6b+30ax5b2+30ax4b3+15ax3b4+3ax2b5+3x6a2+15x5a2b+30x4a2b2+30x3a2b3+15x2a2b4+3xa2b5+a3(x+b)5
展开 a3(x+b)5:a3x5+5a3x4b+10a3b2x3+10a3b3x2+5xa3b4+a3b5
=x8+5x7b+10x6b2+10x5b3+5x4b4+x3b5+3ax7+15ax6b+30ax5b2+30ax4b3+15ax3b4+3ax2b5+3x6a2+15x5a2b+30x4a2b2+30x3a2b3+15x2a2b4+3xa2b5+a3x5+5a3x4b+10a3b2x3+10a3b3x2+5xa3b4+a3b5