解答
展开 (x+y)16
解答
x16+16x15y+120x14y2+560x13y3+1820x12y4+4368x11y5+8008x10y6+11440x9y7+12870x8y8+11440x7y9+8008x6y10+4368x5y11+1820x4y12+560x3y13+120x2y14+16xy15+y16
求解步骤
(x+y)16
使用二项式定理: (a+b)n=i=0∑n(in)a(n−i)bia=x,b=y
=i=0∑16(i16)x(16−i)yi
展开求和
=0!(16−0)!16!x16y0+1!(16−1)!16!x15y1+2!(16−2)!16!x14y2+3!(16−3)!16!x13y3+4!(16−4)!16!x12y4+5!(16−5)!16!x11y5+6!(16−6)!16!x10y6+7!(16−7)!16!x9y7+8!(16−8)!16!x8y8+9!(16−9)!16!x7y9+10!(16−10)!16!x6y10+11!(16−11)!16!x5y11+12!(16−12)!16!x4y12+13!(16−13)!16!x3y13+14!(16−14)!16!x2y14+15!(16−15)!16!x1y15+16!(16−16)!16!x0y16
化简 0!(16−0)!16!x16y0:x16
化简 1!(16−1)!16!x15y1:16x15y
化简 2!(16−2)!16!x14y2:120x14y2
化简 3!(16−3)!16!x13y3:560x13y3
化简 4!(16−4)!16!x12y4:1820x12y4
化简 5!(16−5)!16!x11y5:4368x11y5
化简 6!(16−6)!16!x10y6:8008x10y6
化简 7!(16−7)!16!x9y7:11440x9y7
化简 8!(16−8)!16!x8y8:12870x8y8
化简 9!(16−9)!16!x7y9:11440x7y9
化简 10!(16−10)!16!x6y10:8008x6y10
化简 11!(16−11)!16!x5y11:4368x5y11
化简 12!(16−12)!16!x4y12:1820x4y12
化简 13!(16−13)!16!x3y13:560x3y13
化简 14!(16−14)!16!x2y14:120x2y14
化简 15!(16−15)!16!x1y15:16xy15
化简 16!(16−16)!16!x0y16:y16
=x16+16x15y+120x14y2+560x13y3+1820x12y4+4368x11y5+8008x10y6+11440x9y7+12870x8y8+11440x7y9+8008x6y10+4368x5y11+1820x4y12+560x3y13+120x2y14+16xy15+y16